Characterization of rat testicular guanylate cyclase during development

The biochemical characteristics of rat testicular guanylate cyclase were investigated and the activity and subcellular distribution of the enzyme was determined during testicular development. Examination of the effects of metal ions, nucleotides, detergents and other in vitro activators on the activity of guanylate cyclase revealed that the testicular enzyme is similar in most respects to guanylate cyclase isolated from other mammalian tissues. Changes in the total activity of guanylate cyclase during testicular development paralleled changes in the tissue concentration of cyclic GMP; i.e. guanylate cyclase activity and tissue cyclic GMP were highest during the early stages of development. Subcellular fractionation revealed that the activity of the soluble form of guanylate cyclase was best correlated with tissue cyclic GMP. Biochemical analysis of the soluble enzyme prepared from testes of neonatal and adult rats did not reveal any significant differences in the characteristics of the enzyme during ontogeny with the exception of a 2.5 fold increase in V noted in the neonatal testis. The results of this study are consistent with a molecular mechanism that allows independent regulation of the different forms of guanylate cyclase.