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 calcium release channel of the sarcoplasmic reticulum from rabbit skeletal muscle was investigated using both tension recording from skinned fibres 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 skinned fibres, but potentiated caffeine-induced tension. Maximum potentiation was observed with 0.05-0.5% BSA, BSA (0.1%) had no detectable effect on the basal activity of the Ca2+-release channel incorporated in lipid bilayer. However, channel stimulation elicited by either caffeine (2 mM) or ATP (60 mu M) was further enhanced by BSA (0.1%), as indicated by significant increases in P-o, the open probability of the channel. These results suggest that BSA can modulate the response of the skeletal muscle SR Ca2+-release channel to different activators such as caffeine and ATP.