Pituitary adenylate cyclase-activating peptide in the adrenal gland of mammals: distribution, characterization and responses to drugs.

The occurrence, cellular distribution and nature of the 27-amino acid form of pituitary adenylate cyclase-activating peptide (PACAP-27) in the adrenal glands of mammals was investigated by means of immunohistochemistry, radioimmunoassay and chromatography. The concentrations (pmol/g wet weight) of PACAP-27-like immunoreactivity (LI) varied considerably between the species examined: mouse (n = 8), 12.1 +/- 2.0; hamster (n = 4), 9.1 +/- 1.5; rat (n = 13), 2.0 +/- 0.3; cow (n = 3), 0.8 +/- 0.1, and pig (n = 5), 0.7 +/- 0.1. Upon HPLC, the immunoreactivity in extracts of rat, mouse and hamster adrenals coeluted with synthetic PACAP-27 while the immunoreactivity in extracts of cow and pig adrenals eluted as less hydrophobic material. Immunohistochemistry revealed the presence of PACAP-27-LI in the noradrenaline-storing chromaffin cells of the adrenal medulla. No nerve fibers exhibiting PACAP-27-LI could be detected. The effects of drug administration in vivo on the stores of PACAP-27-LI in the rat adrenal were studied and compared with the effects on the adrenal stores of neuropeptide Y (NPY)-LI. Splanchnic activation following insulin-induced hypoglycemia elicited a 41% depletion of NPY-LI 2 h after insulin injection, while the concentrations of PACAP-27-LI remained unchanged. Two days after reserpine administration the stores of PACAP-27-LI and NPY-LI were depleted by 62 and 41%, respectively. Two days later, the concentrations of NPY-LI were increased to 216% of controls, while the concentrations of PACAP-27-LI were similar to that of controls.(ABSTRACT TRUNCATED AT 250 WORDS)