title: Zinc-induced alterations in contractile properties of rat diaphragm muscle in vitro.
abstract: The effect of zinc ions on the isometric contraction of rat diaphragm muscles in the presence and in the absence of external calcium was studied. Using a transducer, the isometric force was measured as a function of supramaximal electrical stimulation, either directly or indirectly applied to the muscle. The following parameters were measured: peak twitch tension, PT, twitch contraction time, CT, relaxation half-time, RT-1/2, and peak rates of tension increase and decrease, +dP/dt and -dP/dt. The following zinc-induced alterations were observed: an increase of the PT; a decrease of the RT-1/2; an increase in the +dP/dt and -dP/dt. The CT was not changed significantly. Our results suggest that zinc ions have a positive inotropic effect on isolated diaphragm muscle. The increase in PT may be explained by a zinc-activated Ca2+ uptake by sarcoplasmic reticulum. This was followed by an increase in the rate of rise of tension development, which was secondary to increased -dP/dt. The mechanism(s) by which extracellular Ca2+ contributes to this action of zinc is not known.
authors.affiliation: Department of Physiology, Faculty of Medicine, University of Erciyes, Kayseri, Turkey.
authors.forename: A
authors.initials: A
authors.lastname: Gölgeli
authors.forename: N
authors.initials: N
authors.lastname: Dursun
authors.forename: C
authors.initials: C
authors.lastname: Süer
authors.forename: C
authors.initials: C
authors.lastname: Ozesmi
authors.forename: S
authors.initials: S
authors.lastname: Aydogan
mesh_terms: D000818:Animals; D002118:Calcium / Q000494:pharmacology / Q000502:physiology*; D003964:Diaphragm / Q000187:drug effects*; D004558:Electric Stimulation; D007537:Isometric Contraction / Q000187:drug effects*; D008297:Male; D009469:Neuromuscular Junction / Q000187:drug effects; D010791:Phrenic Nerve / Q000502:physiology; D051381:Rats; D009435:Synaptic Transmission / Q000187:drug effects; D015032:Zinc / Q000633:toxicity*
chemical_list: D015032:Zinc; D002118:Calcium