RIN m5F (Rat Insulinoma) Cells Possess Receptors for Atrial Natriuretic Peptide (ANP) and a Functioning cGMP System

Atrial natriuretic peptide (ANP) has been shown to be present in rat plasma as fragment (ANP-(99-126)) containing 28 amino acids {Schwartz, Getter, Manning, Siegel, Fok, Smith and Needleman 1985). ANP exerts a wide spectrum of cardiovascular, renal and endocrine actions (reviewed by Weidman, Gnadinger, Ziswiler, Shaw, Bachmann, Rascher, Uehlinger, Hosier and Reubi 1986): ANP increases circulating insulin levels by 50% while plasma glucose levels remain unaffected (Weidmann et al. 1986; Weidmann, Hellmiller, Uehlinger, Lang, Gnddiger, Hasler, Shaw and Bachmann 1986a). After binding to specific receptors in various cells ANP activates a particulate guanylate cyclase which extremely elevates cGMP levels (Winquist, Faison, Waldman, Schwarz, Murad and Rapoport 1984; Gerzer, Tremblay, Pang, Vinay, DeLean and Hamet 1985). It can be speculated whether the aforementioned elevation of plasma insulin levels is a direct or indirect effect of ANP. Insulin-secreting cell lines from the rat are a convenient model for studies of hormone release mechanisms (Wollheim and Pozzan 1984). It was the aim of the present study (first) to prove an ANP-sensitive cGMP system in RIN m5F cells and (second) to investigate a possible direct effect of ANP via ANP receptors on insulin release.