EFFECT OF BOVINE SERUM-ALBUMIN ON THE CALCIUM-RELEASE CHANNEL OF SARCOPLASMIC-RETICULUM FROM RABBIT SKELETAL-MUSCLE

The effect of bovine serum albumin (BSA) on the activity of the calciu m release channel of the sarcoplasmic reticulum from rabbit skeletal m uscle was investigated using both tension recording from skinned fibre s and electrophysiological recording of unitary channel currents from planar lipid membranes, BSA had no effect on the Ca2+ affinity of the contractile proteins, elicited no tension per se in Ca2+-loaded skinne d fibres, but potentiated caffeine-induced tension. Maximum potentiati on was observed with 0.05-0.5% BSA, BSA (0.1%) had no detectable effec t on the basal activity of the Ca2+-release channel incorporated in li pid bilayer. However, channel stimulation elicited by either caffeine (2 mM) or ATP (60 mu M) was further enhanced by BSA (0.1%), as indicat ed by significant increases in P-o, the open probability of the channe l. These results suggest that BSA can modulate the response of the ske letal muscle SR Ca2+-release channel to different activators such as c affeine and ATP.