052 



PHYSIOLOGY OF GONADS 



The various tissues of the body respond in 

 quite different degrees to the several hor- 

 mones. This difference in response is es- 

 pecially marked with the sex hormones. 

 Those tissues which respond dramatically 

 to the administration of a hormone are 

 termed the "target organs" of that hor- 

 mone. Just what, at the cellular level, dif- 

 ferentiates a target organ from the other 

 tissues of the body is not known exactly 

 but there is evidence that each kind of tis- 

 sue is characterized by a certain pattern of 

 enzymes. The pattern of enzymes is estab- 

 lished, by means as yet unknown, in the 

 course of embryonic differentiation. The 

 enzyme glucose 6-phosphatase, which hy- 

 drolyzes glucose 6-phosphate and releases 

 free glucose and inorganic phosphate, is 

 present in liver but absent from skeletal 

 muscle. Even though a given reaction in 

 two different tissues may be mediated by 

 what appears to be the same enzyme, the 

 enzymes may be different and subject to 

 different degrees of hormonal control. Hen- 

 ion and Sutherland (1957) showed that the 

 phosphorylase of liver responds to glucagon 

 but the phosphorylase of heart muscle does 

 not. Further, the two enzymes are immuno- 

 logically distinct. An antiserum to purified 

 liver phosphorylase will not react with heart 

 phosphorylase to form an inactive antigen- 

 antibody precipitate, but it does react in 

 this manner with liver phosphorylase. Fur- 

 ther, perhaps more subtle, differences be- 

 tween comparable enzymes from different 

 tissues have appeared when lactic dehydro- 

 genases from liver, heart, skeletal muscle, 

 and other sources were tested for their rates 

 of reaction with the several analogues of the 

 pyridine nucleotides now available (Kap- 

 lan. Ciotti, Hamolsky and Bicbcr, 1960). 

 p]xtension of this technique may reveal dif- 

 ferences in response to added hormones. 



In addition to these differences in the re- 

 sponse to a hormone of the tissues of a 

 single animal, there may be differences in 

 the response of the comparable tissues of 

 different species to a given dose of hormone. 

 Estrone, estriol, and other estrogens have 

 different potencies relative to estradiol in 

 different species of mammals. There are 

 slight differences in the amino acid se- 

 quences of the insulins and vasopressins 

 from flifferent species and quite marked 



differences in the chemical structure (Li and 

 Papkoff, 1956) and physiologic activity 

 (Knobil, Morse, Wolf and Greep, 1958) 

 of the pituitar}^ growth hormones of cattle 

 and swine, on the one hand, and of pri- 

 mates, on the other. 



A. ESTROGENS 



The amount or activity of certain en- 

 zymes in the target organs of estrogens 

 has been found to vary with the amount of 

 estrogen present. Examples of this phe- 

 nomenon are /^-glucuronidase (Odell and 

 Fishman, 1950) , fibrinolysin (Page, Glen- 

 dening and Parkinson, 1951), and alkaline 

 glycerophosphatase (Jones, Wade, and 

 Goldberg, 1953). Kochakian (1947) re- 

 ported that the amount of arginase in the 

 rat kidney increased after the injection of 

 estrogens. Enzyme activity is increased by 

 other hormones as well; for example, pro- 

 gesterone has been found to increase the 

 activity of phosphorylase (Zondek and 

 Hestrin, 1947) and of adenosine triphos- 

 phatase (Jones, Wade, and Goldberg, 1952). 



In most experiments the amount of en- 

 zyme present has been inferred from its 

 activity, measured chemically or histo- 

 chemically under conditions in which the 

 amount of enzyme is rate-limiting. This 

 does not enable one to distinguish between 

 an actual increase in the number of mole- 

 cules of enzyme present in the cell and an 

 increase in the activity of the enzyme mole- 

 cules without change in their number. A 

 few enzymes can be measured by some 

 other property, such as absorption at a 

 specific wavelength, by which the actual 

 amount of enzyme can be estimated (see 

 review by Knox, Auerbach, and Lin, 1956). 

 Knox and Auerbach (1955) found that the 

 activity of the enzyme tryptophan peroxi- 

 dase-oxidase (TPO) of the liver was 

 decreased in adrenalectomized animals and 

 increased by the administration of corti- 

 sone. Knox had shown previously that 

 th(> administration of the substrate of 

 the enzyme, tryptophan, would lead 

 to an increase in the activity of the en- 

 zyme which was maximal in 6 to 10 

 hours. Evidence that the increased activity 

 of enzyme following the administration of 

 cortisone represents the synthesis of new 

 protein molecules is supplied by experi- 



