Phencyclidine block of Ca 2+ ATPase in rat heart sarcoplasmic reticulum

• Published in: Toxicology (Amsterdam) Vol. 129; no. 2; pp. 95 - 102
• Main Authors: Pande, M., Cameron, J.A., Vig, P.J.S., Desaiah, D.
• Format: Journal Article
• Language: English
• Published: Elsevier Ireland Ltd 1998
• Subjects: Ca 2+ ATPase; Heart; Inhibition; Rat; Sarcoplasmic reticulum; Heart; Rat; Sarcoplasmic reticulum; Ca 2+ ATPase; Inhibition
• ISSN: 0300-483X; 1879-3185
• DOI: 10.1016/S0300-483X(98)00061-4

Phencyclidine hydrochloride (PCP) also known as Angel Dust is a very potent psychotomimetic drug of abuse. Besides its central nervous system (CNS) effects PCP produces a number of adverse effects in a variety of tissues including the cardiovascular system. Since PCP is known to alter the cellular calcium homeostasis the present studies were initiated to determine the changes in cardiac Ca 2+ ATPase activity in rats treated with PCP. For in vitro studies the cardiac sarcoplasmic reticulum (SR) fractions prepared from normal rats were incubated with 25, 50 and 100 μM PCP and the enzyme activities were estimated. Whereas, for in vivo studies the cardiac SR fractions prepared from rats treated with PCP (10 mg/kg body wt. single dose, intra-peritoneally (i.p.)) and sacrificed at different time intervals were used. PCP reduced the Ca 2+ ATPase activity significantly both in vitro and in vivo. A 50% inhibition of the enzyme activity was obtained with 100 μM PCP in vitro. A significant reduction of SR Ca 2+ ATPase was also evident as early as 1 h after treatment of rats with PCP. The reduction of Ca 2+ ATPase activity in SR was irreversible even at 12 h after treatment. The in vitro kinetic studies revealed that PCP was found to be a competitive inhibitor of Ca 2+ ATPase with respect to the substrate, ATP, and non-competitive with respect to Ca 2+ activation. These results indicate that PCP alters the myocardial Ca 2+ homeostasis by inhibiting the Ca 2+ ATPase in cardiac SR in rats. Inhibition of SR Ca 2+ ATPase may result in the impairment of contraction and relaxation coupling processes in the myocardium.