EXPRESSION OF PITUITARY ADENYLATE-CYCLASE ACTIVATING POLYPEPTIDE (PACAP) GENE BY RAT SPERMATOGENIC CELLS

Pituitary adenylate cyclase activating polypeptide (PACAP) a neuropept ide recently isolated from hypothalamus, exists in two biological acti ve forms: PACAP38 and PACAP27. The PACAP precursor (preproPACAP) conta ins besides PACAP a 29 amino acid peptide designated PACAP related pep tide (PRP) in its sequence. The hypothalamus has the highest concentra tion of PACAP, but PACAP mRNA and immunoreactivity are found in severa l other tissues including the testis. Here we demonstrate that extract s of testis contain all preproPACAP derived peptides the concentration s being: PACAP38 2.8 +/- 0.14 pmol/g wet weight, PACAP27 0.18 +/- 0.02 pmol/g and PRP 0.84 +/- 0.14 pmol/g, respectively. By in situ hybridi zation PACAP/PRP mRNA was located near the perimeter of the seminifero us tubules in early germ cells, and by immunocytochemistry PACAP immun oreactivity was shown in spermatids near the lumen, in spermatogonia a nd primary spermacytes, but not in mature spermatids or spermatozoa. T he findings suggest that PACAP might be an autocrine regulator in deve loping germ cells during spermatogenesis.