Regulation of calcitonin gene-related peptide mRNA expression in the hearts of spontaneously hypertensive rats by testosterone.

Previous studies have demonstrated the existence of calcitonin gene-related peptide (CGRP)-immunoreactive nerve fibres and nerve cell bodies in the rat heart. Using polymerase chain reaction we have investigated whether CGRP messenger RNA (mRNA) could be detected in heart tissue of spontaneously hypertensive rats, and whether CGRP-mRNA levels are affected by gonadectomy and testosterone substitution. Two weeks after castration CGRP-mRNA levels decreased to 65.2 +/- 6.4% of control values, whereas daily dihydrotestosterone substitution reversed this effect (88.0 +/- 1.2% of control). Our results indicate that steroid hormones control the expression of intracardiac CGRP on a pretranslational level.