Highly Specific Testicular Adenosine 3',5'*–Monophosphate Phosphodiesterase Associated with Sexual Maturation

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Abstract
Adenosine 3',5'—monophosphate (cyclic AMP) is known to be the intracellular mediator of the action of several hormones. Both ICSH and FSH have been shown to increase testicular cyclic AMP concentration. Cyclic AMP has been shown to increase the production of testosterone by the perfused testis. The effective concentration of cyclic AMP is determined both by its rate of synthesis and its rate of degradation effected by cyclic nucleotide phosphodiesterase (PDE). Seven separate isoenzymes of cyclic nucleotide phosphodiesterase (labeled a—g) are present in tissues of rat and rabbit. The adult rat testis contains the c and f components; the f component is only found in the testis. In the 20–day—old rat only the c component is present. The f component begins to appear at 40 days of age and reaches adult levels by 50 days of age. Histological sections show spermatids present at 30 days and mature spermatozoa at 50 days of age. Total PDE activity increased 5—fold from day 20 to day 50. This increase in PDE activity is paralleled by an identical increase in testicular adenyl cyclase activity during the same time period. Kinetic analysis of PDE indicates that the c component has a Km for cyclic AMP of 6.5 X 10-5M and a Km for cyclic GMP of 6.8 X 10-5M. The f component has a Km for cyclic AMP of 2.5 X 1O-6M, some 24–fold lower. Thus, the specific isozyme associated with sexual maturation appears to be mainly a cyclic AMP phosphodiesterase. (Endocrinology91: 716, 1972)

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