Biological Regulation of Testicular Angiotensin I-Converting Enzyme

Summary

Angiotensin I-converting enzyme (ACE) from rat testes and lung was purified to homogeneity and partially characterized with respect to physicochemical parameters. Additionally, the biological regulation of testicular ACE by gonadotropins and androgens was investigated and the cell type with which ACE is associated in testes was identified. Rat testicular ACE is a lower molecular weight, isozymic version of the lung enzyme. Partial proteolysis of each isozyme produces different peptide maps, suggesting unique primary structures for each protein. The sensitivity of each isozyme to Co²⁺, chelators and thermal denaturation is different, a finding that further supports the hypothesis that structural differences exist between the two isozymes. The pituitary gland is essential for the development during puberty and maintenance during adulthood of testicular ACE. In hypophysectomized mature rats, gonadotropins or androgen can maintain ACE activity to near sham-operated levels. ACE activity in testes appears to be associated almost entirely with various stages of germinal cell development. The function(s) of testicular ACE awaits definition. The mechanism of androgen-maintenance of testicular ACE is unclear. Whether androgen specifically induces gene expression of testicular ACE or simply allows for ACE activity to develop in parallel with spermatogenesis is an unresolved question.