The Actions of Growth Hormone and Prolactin on Rat Hepatocytes are not Mediated by Changes in Cytoplasmic Ca2+

Abstract

In connection with measurement of the binding of growth hormone and prolactin to rat hepatocytes we investigated whether such binding is associated with changes in the cytoplasmic Ca²⁺ concentration. Whereas hepatocytes from male animals were found to have essentially only somatogenic receptors, lactogenic receptors were dominant in females. All hepatocyte preparations responded to epinephrine and vasopressin with transient peaks of cytoplasmic Ca²⁺. However, no effects on cytoplasmic Ca²⁺ were obtained when cells from female or male animals were exposed to growth hormone or prolactin. We therefore conclude that signal transduction of the growth hormone and prolactin responses in the rat liver does not involve an early messenger function for Ca²⁺.