title: Role of calcium current and sarcoplasmic reticulum calcium release in control of myocardial contraction in rat and rabbit myocytes.
abstract: The relative importance of calcium current and sarcoplasmic reticulum in supplying contraction-related calcium was investigated in isolated rat and rabbit cardiac ventricular myocytes using patch-clamp and video techniques. Calcium current and contractile response were manipulated via variation of [Ca2+]o between 0.25 and 8.0 mM. Sarcolemmal calcium influx was derived from integration of the calcium current. An increase in [Ca2+]o from 0.25 to 8 mM augmented the amplitude of contractile shortening from 7 to 375% of control (amplitude at 1.0 mM) in rat but only from 36.5 to 177.6% in rabbit. Upon variation in [Ca2+]o from 0.5 to 8.0 mM calcium current increased from 67 to 175% of control in rat and from 65 to 150% in rabbit. Sarcolemmal calcium influx in rat was, however, only about half of that in rabbit for the entire range of [Ca2+]o and saturated at [Ca2+]o over 2.0 mM in both species. Application of 1 microM ryanodine increased calcium current and slowed its inactivation time course in the rat, but in the rabbit a slight decrease in current was observed and the inactivation time course was not obviously affected. The sarcoplasmic reticulum calcium release:transsarcolemmal calcium flux ratio is at least four-fold greater in the rat than in the rabbit. The results from this study further explain the well-known marked differences in contractile control in the two species.
authors.affiliation: Department of Medicine, UCLA School of Medicine 90024.
authors.forename: S Y
authors.initials: SY
authors.lastname: Wang
authors.forename: L
authors.initials: L
authors.lastname: Winka
authors.forename: G A
authors.initials: GA
authors.lastname: Langer
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism*; D015220:Calcium Channels / Q000502:physiology*; D006352:Heart Ventricles / Q000166:cytology; D066298:In Vitro Techniques; D008297:Male; D009200:Myocardial Contraction / Q000502:physiology*; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D012519:Sarcoplasmic Reticulum / Q000378:metabolism*
chemical_list: D015220:Calcium Channels; D002118:Calcium