title: Membrane currents elicited by porcine vasoactive intestinal peptide (VIP) in follicle-enclosed Xenopus oocytes.
abstract: Membrane currents were recorded from voltage-clamped Xenopus laevis oocytes, surrounded by their enveloping follicular and epithelial cells. Porcine vasoactive intestinal peptide (VIP) generated a membrane current due to an increase in membrane conductance to K+. The VIP current was mimicked by the adenylate cyclase activator forskolin and was potentiated by phosphodiesterase inhibitors, suggesting that adenosine 3',5'-cyclic monophosphate (cyclic AMP) plays a role in mediating the response. Though resembling the follicle's responses to catecholamines and adenosine in ionic basis and apparent mechanism, the response to VIP was not blocked by catecholaminergic or purinergic antagonists, indicating the presence of a specific VIP receptor in the follicle. Among the VIP related peptides, PHM-27 generated similar but smaller K+ currents and porcine secretin and glucagon neither elicited a response nor blocked that to VIP. After treating follicles with collagenase to remove the epithelial and follicular cells the responses to VIP were either substantially reduced or abolished, suggesting that the VIP receptors and K+ channels are both located in the follicular cells.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009865:Oocytes / Q000187:drug effects / Q000502:physiology*; D010451:Peptide PHI / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011964:Receptors, Gastrointestinal Hormone / Q000187:drug effects / Q000502:physiology*; D018005:Receptors, Vasoactive Intestinal Peptide; D013552:Swine; D013806:Theophylline / Q000494:pharmacology; D014660:Vasoactive Intestinal Peptide / Q000494:pharmacology*; D014982:Xenopus laevis / Q000502:physiology*
chemical_list: D010451:Peptide PHI; D011964:Receptors, Gastrointestinal Hormone; D018005:Receptors, Vasoactive Intestinal Peptide; D014660:Vasoactive Intestinal Peptide; D013806:Theophylline; D000242:Cyclic AMP; D011188:Potassium; D015056:1-Methyl-3-isobutylxanthine