Ryanodine-sensitive intracellular Ca2+ stores in isolated rabbit penile erectile tissue.
Norepinephrine release from adrenergic nerve terminals leads to a rise in intracellular Ca2+, which promotes penile smooth muscle contraction and detumescence. Ca2+ sources are the extracellular space and sarcoplasmic Ca2+ stores. To elucidate the role of intracellular stores strips from rabbit erectile tissue were investigated in an organ bath study. Contractions were elicited by phenylephrine (PE) and electrical stimulation. Incubation in Ca(2+)-free solution as well as exposure to nifedipine did not abolish electrical or PE-induced contraction. Ryanodine (10(-5) mol/l), a functional blocker of sarcoplasmic Ca2+ channels, significantly reduced PE response. In the presence of caffeine (10(-3) mol/l) the effect was significantly enhanced. Addition of nifedipine nearly abolished the contraction. These results provide evidence for intracellular Ca2+ pools in cavernosal tissue and indicate that the alpha 1-adrenoceptor-induced contraction requires the opening of voltage-gated Ca2+ channels and the release of Ca2+ from intracellular stores.
Sparwasser
C
C
Veterans Administration Hospital, Madison, WI, USA.
Drescher
P
P
Eckert
R
R
Madsen
P O
PO
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D004558:Electric Stimulation; D066298:In Vitro Techniques; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D009543:Nifedipine / Q000494:pharmacology; D010410:Penile Erection / Q000502:physiology*; D010413:Penis / Q000502:physiology*; D010656:Phenylephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012433:Ryanodine / Q000494:pharmacology*; D012996:Solutions
D012996:Solutions; D012433:Ryanodine; D010656:Phenylephrine; D002110:Caffeine; D009543:Nifedipine; D011188:Potassium; D002118:Calcium