Inotropic and Lusitropic Effects of Calcitonin Gene-Related Peptide in the Heart.

Inotropic and Lusitropic Effects of Calcitonin Gene-Related Peptide in the Heart. Am J Physiol Heart Circ Physiol. 2013 Apr 12; Authors: Al-Rubaiee M, Gangula PR, Millis RM, Walker RK, Umoh NA, Cousins VM, Jeffress MA, Haddad GE Abstract Previous studies have demonstrated positive-inotropic effects of calcitonin gene-related peptide (CGRP) but the mechanisms remain unclear. Therefore, two experiments were performed to determine the physiological correlates of the positive-inotropic effects of CGRP. Treatments designed to antagonize the effects of physiologically-active CGRP 1-37 included post-treatment with CGRP8-37 and pretreatment with LY294002 (LY, an inhibitor of PI3K), 17β-estradiol (E) and progesterone (P) were also used to modulate the effects of CGRP1-37. Experiment 1: In vitro studies on sarcomeres and cells of isolated adult rat cardiac myocytes. CGRP1-37, alone and in combination with E and P, decreased sarcomere shortening velocities and increased shortening percentages, effects that were antagonized by CGRP8-37 but not by LY. CGRP1-37 increased resting intracellular calcium ion concentrations, [Ca2+]i and Ca2+ influxes, effects that were also antagonized by both CGRP8-37 and LY. Experiment 2: In vivo studies on left ventricular pressure-volume (PV) loops. CGRP1-37 increased end-systolic pressure, ejection fraction and velocities of contraction and relaxation while decreasing stroke volume, cardiac output, stroke work, PV area and...
Source: American Journal of Physiology. Heart and Circulatory Physiology - Category: Physiology Authors: Tags: Am J Physiol Heart Circ Physiol Source Type: research