Sarcoplasmic reticulum buffering of myoplasmic calcium in bovine coronary artery smooth muscle.

Abstract

SUMMARY1. We tested the hypothesis that the sarcoplasmic reticulum (SR) buffers (attenuates) the increase in averaged myoplasmic free [Ca2+] (Caim)

Block of large conductance Ca(2+)‐activated K+ channels in rabbit vascular myocytes by internal Mg2+ and Na+.

“…B (Jelicks & Gupta, 1990;Okada, Ishikawa & Saito, 1992;Sturek, Kunda & Hu, 1992;Quamme, Dai & Rabkin, 1993 (Golowasch et al 1986;Trieschmann & Isenberg, 1989;Zhang et al 1995).…”

Spontaneous sarcoplasmic reticulum calcium release and extrusion from bovine, not porcine, coronary artery smooth muscle.

“…The extent of control that the sarcoplasmic reticulum (SR) might have in regulating intracellular Ca2l in vascular smooth muscle is an area of much discussion (Allen & Seidel, 1986). Sturek et al (Sturek et al 1992) demonstrated that the SR in vascular smooth muscle attenuates the increase in myoplasmic free Ca2+ (Caim) resulting from Ca21 influx. This being the case, when the SR is Ca2+-loaded it can no longer sequester the continuing influx of Ca2+ into the cell.…”

“…Recently, three distinct models have beefi proposed to describe the regulation of intracellular Ca2+ by the endoplasmic/sarcoplasmic reticulum (see companion paper (Sturek, Kunda & Hu, 1992) for details). The extent of control that the sarcoplasmic reticulum (SR) might have in regulating intracellular Ca2l in vascular smooth muscle is an area of much discussion (Allen & Seidel, 1986).…”

Handling of Cytoplasmic Ca2+ by the Sarcoplasmic Reticulum during α1-Adrenoceptor-Mediated Contraction of Rat Mesenteric Resistance Arteries

“…It was shown that in microsomes from vas cular smooth muscles, the Ca2+-uptake depended on the free Ca 2+ concentration outside the vesicles (26). Sturek et al (23) showed that when [Ca 2+1 i was higher, the sub sequent caffeine-induced [Ca 2+] i transient was proportion ally larger, indicating a greater Ca 2+ uptake at higher cytoplasmic Ca2+. Therefore, an elevation of [Ca 2+] i due to increased Ca 2+ influx by PE may be associated with the enhancement of Ca 2+ uptake into the SR in the presence of PE.…”

“…As one of the functions of the SR in smooth muscles, the Ca 2+ pump promotes the uptake of Ca2+ influxed from the extracellular space; thereby, the SR works to reduce [Ca 2+] i (22,23). In such a situation, an interven tion to inhibit the SR Ca 2+ pump would increase [Ca 2+] i (24).…”