Rat arterial smooth muscle devoid of ryanodine receptor function: effects on cellular Ca(2+) handling.
The roles of intracellular Ca(2+) stores and ryanodine (Ry) receptors for vascular Ca(2+) homeostasis and viability were investigated in rat tail arterial segments kept in organ culture with Ry (10 - 100 microM) for up to 4 days. Acute exposure to Ry or the non-deactivating ryanodine analogue C(10)-O(eq) glycyl ryanodine (10 microM) eliminated Ca(2+) release responses to caffeine (20 mM) and noradrenaline (NA, 10 microM), whereas responses to NA, but not caffeine, gradually returned to normal within 4 days of exposure to RY: Ry receptor protein was detected on Western blots in arteries cultured either with or without RY: Brief Ca(2+) release events (sparks) were absent after culture with Ry, whereas Ca(2+) waves still occurred. The propagation velocity of waves was equal ( approximately 19 microm s(-1)) in tissue cultured either with or without RY: Inhibition of Ca(2+) accumulation into the sarcoplasmic reticulum (SR) by culture with caffeine (5 mM), cyclopiazonic acid or thapsigargin (both 10 microM) decreased contractility due to Ca(2+)-induced cell damage. In contrast, culture with Ry did not affect contractility. Removal of Ca(2+) from the cytosol following a Ca(2+) load was retarded after Ry culture. Thapsigargin reduced the rate of Ca(2+) removal in control cultured rings, but had no effect after Ry culture. It is concluded that intracellular Ca(2+) stores recover during chronic Ry treatment, while Ry receptors remain non-functional. Ry receptor activity is required for Ca(2+) sparks and for SR-dependent recovery from a Ca(2+) load, but not for Ca(2+) waves or basal Ca(2+) homeostasis.
Dreja
K
K
Department of Physiological Sciences, Lund University, Lund, Sweden.
Nordström
I
I
Hellstrand
P
P
D000818:Animals; D001158:Arteries / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D005260:Female; D015151:Immunoblotting; D066298:In Vitro Techniques; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism; D008861:Microsomes / Q000187:drug effects / Q000378:metabolism; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow / Q000187:drug effects; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects / Q000378:metabolism*; D013623:Tail / Q000098:blood supply
D019837:Ryanodine Receptor Calcium Release Channel; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium