title: Two components in the adrenal nicotinic secretory response revealed by cobalt ramps.
abstract: Prolonged stimulation with nicotine (50 microM) enhanced the secretion of catecholamines from perfused cat adrenal glands. The profile of secretion consisted of a quick activation phase to a peak of 7.68 micrograms/min followed by a second inactivation phase which exhibited a t1/2 of 3.75 min. Sustained stimulation with a solution enriched in K+ (59 mM) also evoked a transient secretory response, with a peak release of 8.62 micrograms/2 min and a t1/2 for inactivation of 4.8 min. Co2+ (10 mM) blocked the nicotinic response by 58% and the K(+)-evoked secretory response by over 96%. In the presence of Co2+ (5 mM), continuous perfusion with nicotine produced a transient but large initial secretory response; the gradual decrease of the extracellular Co2+ concentration, [Co2+]0, as a continuous ramp allowed the development of a second component of secretion which inactivated later on. When the glands were continuously stimulated with 59 mM K+ in the presence of Co2+, the first component of secretion was missing; the second component appeared as [Co2+]0 decreases as a ramp. In similar experiments performed in low-Na+ solution (10 mM Na+), only the first secretion component evoked by nicotine was observed. This finding suggests that the second component of secretion depends on Na+ entry through the nicotinic receptor, on the ensuing cell depolarization and on Ca2+ entry through voltage-dependent Ca2+ channels.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Departamento de Farmacología y Terapéutica, Facultad de Medicina, Universidad Autónoma de Madrid, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Montiel
authors.forename: A R
authors.initials: AR
authors.lastname: Artalejo
authors.forename: P
authors.initials: P
authors.lastname: Sánchez-García
authors.forename: A G
authors.initials: AG
authors.lastname: García
mesh_terms: D000311:Adrenal Glands / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D002395:Catecholamines / Q000378:metabolism*; D002415:Cats; D003035:Cobalt / Q000378:metabolism; D005260:Female; D006207:Half-Life; D066298:In Vitro Techniques; D008297:Male; D009538:Nicotine / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000502:physiology
chemical_list: D002395:Catecholamines; D003035:Cobalt; D009538:Nicotine; D012964:Sodium; D011188:Potassium