Exchange characteristics of the noradrenaline‐sensitive calcium store in vascular smooth muscle cells or rabbit ear artery.

Abstract

3. At the same [Ca]. the degree of filling is higher in K-depolarized tissues than in control tissues. However at 10 mM- [Ca]. and 5-9 mM-K the amount of Ca taken up by the store is larger than that after loading in 0-2 mM-Ca and 141-4 mM-K, although the tissues remain relaxed during loading at 5 9 mM-K and contracted at 141-4 mM-K.4. The Ca antagonists D600 and nicardipine selectively block the contraction induced by K depolarization, but do not affect appreciably the noradrenaline-induced contraction.5. The filling of the store is not significantly reduced by the presence of the Ca antagonists in solutions containing 5-9 mM-K. However these antagonists reduce the degree of filling in K-rich loading solution to a level which is lower than that observed in the control.6. Mn blocks both the contraction induced by K-rich solution and the tonic component of the noradrenaline-induced contraction and it also inhibits filling of the store.7. The results suggest that the filling of the store under physiological conditions occurs by a direct pathway between the store and the extracellular medium.

Effects of calcium entry blockers on calcium‐dependent contractions of rat portal vein

“…The presence of an internal calcium store that can be released by various drugs has been demonstrated previously in vascular smooth muscles (Deth & Van Breemen, 1977;Droogmans et al, 1977;Casteels & Droogmans, 1981). This was usually shown by washing the preparation in a Ca2"-free, EGTA-containing solution and inducing a contraction in response to a supra-maximal concentration of drug.…”

Ketamine‐induced relaxation in intact and skinned smooth muscles of the rabbit ear artery

“…In the rabbit ear artery, in Ca2+-free solution containing 2 mm EGTA, NA produces a contraction due to the release of Ca2 + from intracellular stores (Casteels & Droogmans, 1981). Caffeine also produces a contraction due to the release of Ca2+ from intracellular stores that are closely related to or are the same as those on which NA acts.…”

“…It is known that the intracellular Ca2 + stores are completely filled by this procedure (Casteels & Droogmans, 1981). Thereupon the tissues were superfused for 3 min with Ca2'-free solution and 50 nm NA was then applied for 3 min.…”

A new perspective on the antiatherosclerotic activity of Ca2+‐channel blockers

“…Furthermore, the evidence for direct and rapid entry of extracellular Ca2+ into an antagonist-regulated pool in VSM cells has been reported by Casteels & Droogmans [15]. Consequently, an inhibition of a PDGF-induced PI signal, leading to contraction or mitogenic response to VSM cells by Ca2+ antagonists, would have to occur at the receptor level or at the level of sarcoplasmic reticulum which serves as a pool for Ca2+ being released by the action of IP3.…”