The difference of response of the pituitary glands of male and female albino rats treated with the growth hormone.код для вставкиСкачать
THE IUIFFEBENCE OE’ BESPONXE O F THE PITUITARY GLAKDS O F MALE AND FEMALli: ALBISO RATS TREATED WITH THE GROWTH HORMONE EI. S. RUBINSTEIN Nezcro-A~~atomzcal Laboratory, Department of Anatomy, Cniversity o f Maryland X e d i c a l School I n the course of studies involving the growth hormone, it was noted that the pituitary glands of artificially enlarged animals showed a distinct reactive difference depending upon the sex of the animal, This difference was so striking and interesting that the data were subjected to statistical treatment in order to test their significance. Because in the albino rat differences in pituitary weight occur normally between the sexes, it was deemed advisable to compare the end result with the normal and t o report the findings which appeared to be significant. For this study seventy-four albino rats (Mus norvegicusvar. albinus) from seventeen litters were divided into two large groups, according to s e x Each group was further subdivided into three subgroups, namely, test animals and two sets of controls. The test subgroup was composed of the lightest animals of each litter while the heaviest animals were inclnded in the control subgroup which remained uninjected. I n addition, animals intermediate in weight were placed in the control subgroup which ~ 7 a sto receive a non-specific meat extract. T h e n thus divided the seventy-€our animals were arranged as shown in column 1 of table 1. All animals were kept under laboratory conditions similar to those previously described ( Rubinstein, ’32). The differences in initial body weight may also be seen in table 1, from which it may be noticed that both the test ani131 132 H. S. RUBINSTEIS mals and the meat injected controls were significantly lighter than the uninjected controls, although, as may be judged from the critical ratios,1 this significance was greater f o r the test animals. At the beginning of the experiment all animals had already reached the adult state, being 6 to 8 months of age. They were thus chosen because it had previously been found that rats growing normally in the early growth period failed to respond markedly to the added growth hormone (Rubinstein, '33). TABLE 1 Slaowmg the grouping of the animals and the tnitial body weights for all groups MEAN I N I T I A L BODY WEIQHT 3 1 aiiimals Males : 11 test animals 10 uiiiiijected controls 10 meat injeeted eontrols 247.9 & 3.32 278.7 k 3.30 266.1 If: 3.32 43 aiiimals Females : 16 test aiiimals 1 2 uniqjeeted coiitrols 16 meat injected controls 183.3 k 2.30 201.5 f 2.60 190.2 f 1.58 DEVIATION FROM UNTNJECTED COXTROI; CRITICAL RATIO - 30.8 2 4.7 6.56 - 12.6 f 4.7 2.68 - 18.2 f 3.4 5.35 - 11.3 k 3.1 3.64 The test animals mere injected intraperitoneally daily (except Sunday) with 2 ec. of growth hormone prepared as an aqueous alkaline extract from the anterior lobe of fresh beef pituitaries. This extract was similar to that employed in other growth studies, and the details of its preparation have been reported elsewhere (Rubinstein and Fox, '34). The injections were continued for 22 weelis, but active differential growth response was obtained only after the ninth week because of the impotence of the extract used during the 'By critical ratio is meant t h a t figure which results froin dividing the differeiice between the coiitrol aiid test observations by the probable error of this difference. A critiral ratio of 3 or more has been coiisiderec? as evideiice o f a significant difference. DIFFERENTIAL BESPONSE O F PITUITAEY 133 earlier period of the experiment. The meat extract used was prepared exactly as the pituitary extract and was merely employed to prove that the growth response noted in the test animals was not due to a food factor but represented a specific reaction t o the growth stimulating factor of the pituitary gland. At the end of the experiment all animals were anesthetized with ether and sacrificed by bleeding through the carotid arteries. This method of exitns was used because it had been found advantageous in other experiments (Rubinstein, '32) where a minimal quantity of blood was desired in ihe TABLE 2 Showing t h e mean final body weights f o r all grou,ps N E A N FINAL BODY W E I G H T D ETI A TI ON FROM UNINJECTED CONTROL CRITICAL RATIO gm. Males : Test animals Uiiiiijeeted controls Meat iiijccted controls 365.7 f 3.98 322.6 k 4.43 309.7 & 4.50 Females : Test animals TJniiijected controls Meat injected controls 296.1 & 4.48 220.4 f 3.18 208.9 f 1.97 43.1 t 5.92 7.3 - 12.9 f 6.31 2.1 75.7 -t- 5.48 13.8 - 11.5 f 3.74 3.1 tissue to be studied. The skulls were opened from above and the brains removed. The pituitary glands were then recovered from the sclla turcica and immediately weighed in a weighing bottle to within a tenth of a milligram. RESULTS A t the end of the experiment all tesl anirrials had become definitely heavier than their two sets of controls, as may be judged from table 2 where it may be noted that while the initial difference between the two sets of controls remained the same (compare with table 1)at the end of the experiment, a marked change had occurred between the test animals and 134 H. S. RUBIFSTEIN both controls. The unchanged differences and critical ratios of the control groups suggest a parallelism in the slope of the growth curve for these groups and, indeed, when plotted out such was found to be the case. On the other hand, the change in the sign of the deviation from a minus to a plus for the test animals shows how much larger the slopes of their growth curpes had become. The significance of this difference may be noted from the critical ratios of this table (2). These differences in growth may be more immediately appreciated from table 3, which gives the average body weight changes f o r all groups during the course of the experiment. TABLE 3 Showing the mean body wright increases for all groups MEA?S QAIW IN GRAMS Males : Test animals Uuiiijected controls Meat injected controls 117.80 f4.87 43.90 e 4.10 43.56 -t- 3.66 Females : Test animals Uniiijected controls Meat injected controls 113.5 f 4.49 18.9 f 1 . 9 i 18.7 2 1.33 D E V I A T I O N FROM UNJNJECTED CONTROL CRITIC.4L RATIO -+ 6.40 11.53 - 0.34 k 5.48 0.06 94.6 +- 4.89 19.34 - 0.20 2 2.38 0.84 73.9 It may be noted that while the male and female test animals gained about 74 and 95 gm. over their respective controls, the differences noted between the controls are insignificant. The larger gain on the part of the test females is not mere chance since it has been consistently noted in all growth experiments in this and other laboratories ( Rubinstein, '32 ; Rubinstein and Kolodner, '34; Johnson and Hill, '30, in the mouse). In addition to the increase noted in body weight, measurements taken of body and tail lengths showed a significant increase in length of the test animals as compared to their controls (Rubinstein, '34). The linear measurerncnts were deemed advisable since it had been previously shown (Downs 135 DIFFERENTIAL RESPONSE O F PITUITARY and Geiling, '29) that some of the increase in body weight (about 8 per cent) was duc to the accumulation of water. Table 4 presents these results quantitatively. Incidently, it may be noted from this table that the tail lengths of the meat injected controls mere significantly shorter than those of the uninjected controls. At any rate, the total length of the test group was definitely increased. A stndy of the pituitary weights R S shown in table 5 disclosed that these averaged 0.0033 gm. heavier in the male test animals than in the uninjected controls. The difference beTABLE 4 Showing meon final body and tail lengths for all groups MEAN FTNATi BODY LENGITII DETIATION FROM CONTROT, 2RITICAL R-4TIO cm. Males : T e s t animals 23.1 2 0.11 Uniiijectcd 21.8 f 0.08 controls Meat injected controls 21.6 f 0.16 Females : Test animals 20.9 f 0.18 Uninjected controls 19.5 f 0.15 Meat injected co~itrols 19.2 f 0.05 DXVIATIOII XEAN F I F A L FROM CONTROL TAIL LENGTH 2RITICAD RATIO em. 1.3 & 0.14 9.30 0.3 f 0.14 19.0 f 0.13 18.7 2.86 t 0.04 - 0.2 2 0.18 1.11 18.6 & 0.04 1.4 2 0.23 6.10 18.9 2 0.05 - 0.1 0.06 1.66 1.0 f 0.11 9.10 0.7 f 0.11 6.36 Z? 17.9 k 0.10 - 0.3 f 0.16 1.88 17.2 k 0.04 - tween the two control groups was insignificant. I n the females, on the other hand, the test animals possessed pituitary glands which averaged 0.0003 gm. below those of the nninjected controls. This difference, as shown by the small critical ratio (0.43) is insignificant. Howcver, when the pituitary glands are considered between the two sets of female controls it may be noted that the difference is 0.0021 gm. in favor of the uninjected controls. 0.00073 This difference divided by its probable error of leads to the significant ratio of 2.88 (almost 3), SO that the difference is significant. 136 H. S. RUBINSTEIN I n order to better appreciate the relations of the initial and final body weights t o the pituitary weights, table 6 has been constructed in which these are tabulated together with TABLE 5 Showing the mean pituitary weight for all groups. A f t e r 40 to 50 days the f e n a l e hypophysis norrtmlly becomes heavoer than the males and the diferences gradually increase DEVIATION FROBS UNINJECl’SD CONTROL MEAN PITUITARY WEIGHT CRIT,OAIi RATIO gm. Males : Test animals Uniiijected eoiitroh Meat injected controls 0.0134 f 0.00041 0.0101 0.00022 0.0102 f 0.00037 * 0.0033 -C 0.00047 7.03 0.0001 t 0.00043 0.23 - 0.0003 & 0.00069 0.43 - 0.0021 2.88 Females : % 0.00073 TABLE 6 Showing the relations of the initial and final body weights t o the observed and tabular pituitary weights. The observed pittiitary weights correspond t o the final body weights while the tabular pituitary weights are t a k m from Donaldson’s table 148 and are tabulated t o correspond with the initial and final body weights. T h i s table 6 seems t o denote a retardation in the growth of the hypophysis of the test female and also suggests a retardation i n the meat injected female ~ BODY W E I G H T I N GRAMS PITUITARY W E I G H T I N GRAMS Table 148 (Donaldson) Initial Final _ _ Observed _ ~ Males : Test animals Uidnjected coiitrols Meat injected controls 247 278 266 366 323 310 0.0134 0.0101 0.0102 0.0097 0.0094 Females : Test animals Uiiiiijected controls Meat injected controls 153 201 190 296 220 209 0.0152 0.0155 0.0134 0.0124 0.0139 0.0131 ;::::,0 ~ 0.0212 0.0163 0.0145 DIFFERENTIAL EESPONSE O F PITUITARY 137 €he approximate tabular pituitary weights corresponding to these body weights. The tabular pituitary weights were taken from table 148 of Donaldson’s ‘The Rat.’ From this table it may be seen that the observed mean pituitary weight of the male test animals (0,0134) is definitely heavier than that which is computed as normal, (0.0122) while the observed pituitary weights of the two sets of controls are below the corresponding final tabular weights. I n the female groups, the observed pituitary weights of the test and meat injected animals appear to be retarded in comparison with the final tabular normals. The mean observed pituitary weight of the uninjected controls (0.0155) agrees quite closely with that considered normal (0.0153) for the observed final body weight. DISCUSSION The pituitary gland of the albino rat for the first 40 or 50 days of life has the same weight in the two sexes. Thereafter, the hypophysis of the female becomes progressively heavier than that of the male so that the difference becomes more and more marked until the plateau of the growth curve is reached. At this time (i.e., at like ages) the pituitary gland of the female is 4 or 5 mg. heavier than that of the male (Donaldson, ’24). That the males of this series compare favorably with these accepted normals may be seen from table 5 from which it may be noted that the hypophysis of the uninjected control females average 5.4 mg. more than that of the males. Whatever the cause for this relatively heavy pituitary gland normal for the female albino rat is, it can only be said at present that it is characteristic for the female albino rat. It does not exist in the wild Norway rat (Mus norvegicns). Noreover, it cannot be correlated purely with albinism since it is absent in the female albino rabbit and guinea pig. Hence, at present this phenomenon cannot be explained, although since Donaldson holds the ‘very heavy hypophvsis in the female’ to be the only outstanding characteristic of the albino rat as an albino-it may be a form of mutation. 138 H. S. RLZBINSTEIN It is of striking interest that the normally smaller pituitary gland of the male, the sex which responds less to the added growth hormone, reacts under test conditions by becoming heavier. On the other hand, the naturally heavier pituitary gland of the normal female, the sex which is more responsive to growth hormone, fails to increase in size and in table 6 appears to be retarded in its growth. Although table 6 shows pituitary weights which are relatively enlarged in the male test animals and retarded in the female test animals and female meat injected animals, table 5 which treats any differences within the observed strain on a statistical basis, discloses the fact that these differences are probably only significant for the male test animals and the female meat injected controls. Even in the latter group, however, the retardation may not be as significant as it first appears. This statement is based on the fact that, as shown in table 2, the significantly smaller meat injected control, may be expected to possess a significantly smaller hypophysis, since normally, pituitary and body weights show a high degree of correlation. Hence, one may conclude from the above that while the pituitary glands of the test males became quite large by thc treatment described, those of the females remained unaltered. The differential response of the glands in the tu7o sexes to similar treatment is quite interesting and has been previously noted in other glands under other experimental conditions. Thus Donaldson (’34) found in his studies on exercise that the thymus became much reduced in the male, not in the female; and the suprarenals became “very large in the female and only slightly affected in the male.” So f a r as experiments carried out with the growth hormone are concerned, it is perhaps interesting t o reflect upon the possible significance of this difference in sex response. It may be that the male albino rat which is growing a t a rapid rate normally as a result of maximum growth efficiency of the pituitary gland can undergo supergrowth only if his pituitary gland is enlarged. I f this is true then the pituitary DIFFEREFTIAL RESPONSE OF PITUITARY 139 gland of the tcst male probably became enlarged through some indirect proccss since there is some evidence at hand (Smith and MacDowcll, '30 ; Collip, '34) which dcmonslrates that endocrine products fail t o directly affect the glands from which they arise. On the other hand, it appears that the normally large pituitary gland of the female albino rat is normally relatively less productive of growth hormone than that of the male for which reason the female responds t o added growth hormone with a greater degree of growth than does the male. The reason f o r the larger pituitary gland in the female is still enigmatic and will only find explanation in the light of further research. While the above suggestions are merely specnlative, not having been proved at this time, it is safe to say that the growth hormone, so f a r as the pituitary size is concerned, tends to restore the predomesticated condition. CONCLUSIONS 1. The pituitary glands of male and female albino rats respond differently to the administration of the growth hormone. 2. I n the adult male, which normally has a smaller pituitary gland than the female, intra-peritoneal administration of the growth hormone enhances body growth and significantly increases the weight of the pituitary gland. 3. I n the adult female in whom the pituitary gland is naturally heavier than that of the male, the growth hormone, similarly administered, leads to a more marked body weight increase than that produced in the male. The pituitary glands of these experimentally enlarged females, however, fail t o increase in weight aiid are retarded in growth. 4. The probable explanations of these phenomena are discussed but their conjectural status f o r the time being is stressed. 140 H. S. RUBINSTEIN ACKNOWLEDGMENTS The author is greatly indebted to Prof. Carl L. Davis, head of this department, who has so generously offered his advice and cooperation throughout this work and to Dr. Henry H. Donaldson f o r his valuable suggestions. L I T E R A T U R E CITED COLLIP,J. B. 1934 Some recent advaiiecs i n the physiology of the anterior pituitary. J. Mt. Sinai Hosp., 1701. 1 , p. 28. DONALDSON, H. II. 1924 The rat. Memoirs of The Wistar Institute of Siiatorny and Biology No. 6. Philadelphia Pa. DONALDSON, H. H. 1934 Persoual communication. DOWNS,W. G., AND E. M. K. GEILING 1929 Possible water balance: The effects of alkaline anterior pituitary extracts. Proc. SOC. Exp. Biol. mid Me&, vol. 27, p. 63. JOHNSON,G. E., AND R. T. HILL 1930 The effect of anterior pituitary extraet 011 the developing albino mouse. Eiidocrinology, vol. 14, p. 400. RUBINSTEIN, H. 8. 1932 The effect of the growth hormone on the brain weightbody weight ratio. Auat. Rec., 1701. 53, p. 265. 1933 The effect of the growth hormone on the early g r o v t h period of the albino rat. Bull. Sch. of Med., U. of Md., vol. 17, p. 163. 1934 The effcct of the growth hormone upon the tail length-body leiigtli ratio of the albino rat. Bull. Sch. of Med., U. of Md., vol. 18, p. 131. RUBINSTEIN, H. S., AND L. 31. Fox 1934 The water and solid contents of the brains of albino rats treated with t h e growth hormone. J. Comp. Neur., vol. 60, p. 349. RUBINSTEIN, H. S.,AND L. J. KOLODNER1934 The effect of the growth hormone 011 body and tail lengths. Anat. Rec., vol. 58, p. 107. SMITH, P. E., AND E. A. MACDOWELL1930 On hereditary anterior pituitary deficiency in the mouse. Anat Rec., vol. 40, p. 249.