Studies on Spermatogenesis in Rats. II. Evidence that Carnitine Acetyltransferase is a Marker Enzyme for the Investigation of Germ Cell Differentiation

Abstract

Levels of carnitine acetyltransferase (CAT) in testes from neonatal rats were approximately 5% of those obtained in testes from adult rats. The changing activities measured during development indicated that maximal rates of increase were achieved at a time when mature primary spermatocytes were being generated. Spermatogonia had lowest CAT levels (0.16 unit/10⁸ cells) while diplotene primary spermatocytes had highest CAT activities (6.1 units/10⁸ cells). The apparent specific activities of other mitochondrial enzymes measured (glutamic dehydrogenase, carnitine palmitoyltransferase, and cytochrome oxidase) in testis did not increase at a time when CAT levels were elevated by over sevenfold.In adult hypophysectomized rats, CAT levels in testes decreased during the regression period, with most rapid rates of loss of activities at times corresponding to the diminution of spermatids and spermatocytes. The CAT activities in testes of fully regressed hypophysectomized rats were low, but were slightly higher than values obtained in testes from 7- and 14-day-old rats. The data were discussed in relation to the use of CAT levels as a biochemical indicator of the relative number of spermatogonia and spermatocytes in rat testes.