A possible role for abscisic acid analogues as calcium channel blockers in mammalian smooth muscle.
1. The abscisic acid (ABA) analogue SD217595 at 10 microM caused inhibition of K(+)-induced phasic and tonic contractions of rat bladder detrusor smooth muscle strips. 2. This attenuation of contraction was a dual effect: the inhibition of phasic contractions was irreversible whereas that of the tonic contractions was readily reversed. 3. The dual inhibition is possibly due to blockade of two subtypes of voltage-operated calcium channels with T- and L-type characteristics. 4. The inhibition of contraction induced by SD217595 is in stark contrast to the potentiation of smooth muscle contraction reported previously with the parent molecule ABA. 5. Two other ABA analogues studied (WL019376 and WL019377) showed neither inhibitory or excitatory effects upon K(+)-induced smooth muscle contraction after short exposures of 10 min.
Lynch
M
M
Division of Biological Sciences, Lancaster University, England.
D000040:Abscisic Acid / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000187:drug effects*; D011188:Potassium / Q000037:antagonists & inhibitors / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D001743:Urinary Bladder / Q000187:drug effects / Q000378:metabolism
D002121:Calcium Channel Blockers; D000040:Abscisic Acid; D011188:Potassium; D002118:Calcium