Effects of adenosine on contractility and 45Ca-uptake in rat urinary bladder.
Effects of adenosine on K+ and ACh-stimulated contractility and 45Ca uptake were studied in the rat urinary bladder smooth muscle and were compared with those of nifedipine. Both adenosine (10(-5) M) and nifedipine (10(-7) M/10(-8) M) significantly inhibited the contractions elicited by K+ (10(-2)-32 x 10(-2) M), Ca2+ (10(-4)-3 x 10(-2 M) in K(+)-depolarized preparations and ACh (10(-9) M-3 x 10(-3) M). Further, adenosine (10(-5) M) significantly (P < 0.05) inhibited K+ (10(-1) M)-stimulated 45Ca-uptake in the bladder strips. However, it had little effect on inward 45Ca movement resulting from ACh (10(-4) M)-induced stimulation. On the other hand, nifedipine (10(-7) M) significantly (P < 0.001) reduced both K+ and ACh-induced 45Ca-uptake in this tissue. It is concluded that the calcium channel blocking action of adenosine is limited to Ca2+ uptake through voltage operated calcium channels, while receptor operated calcium channels activated by muscarinic receptor stimulation appear to be insensitive to the purine.
Parija
S C
SC
Division of Pharmacology and Toxicology, Indian Veterinary Research Institute, Izatnagar.
Raviprakash
V
V
Mishra
S K
SK
D000241:Adenosine / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002132:Calcium Radioisotopes; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D051381:Rats; D001743:Urinary Bladder / Q000187:drug effects* / Q000378:metabolism
D002132:Calcium Radioisotopes; D000241:Adenosine; D002118:Calcium