BOVINE GROWTH-HORMONE INDUCES OSCILLATIONS IN CYTOSOLIC-FREE CA2-RAT HEPATOCYTES( IN SINGLE)

Single rat hepatocytes microinjected with the photoprotein aequorin ge nerate oscillations in the cytosolic free Ca2+ concentration ([Ca2+](i )) when stimulated with agonists acting through the phosphoinositide s ignalling pathway. We show here that, in single rat hepatocytes, bovin e growth hormone (bGH) is able to induce [Ca2+](i) oscillations which display similarities with oscillations induced by phenylephrine. Thus the rate of rise of intracellular Ca2+ in each oscillation closely res embles that induced by Ins(1,4,5)P-3-mediated agonists. However, the d uration of bGH-induced oscillations increases with agonist concentrati on, in contrast to phenylephrine-induced oscillations, which undergo a n increase in frequency as the agonist concentration is raised, withou t any increase in the duration of individual oscillations.