PROLONGED EXPOSURE OF HAMSTERS TO COLD CHANGES THE LEVELS OF G-PROTEINS IN BROWN ADIPOSE-TISSUE PLASMA-MEMBRANES

The levels of G proteins in plasma membranes prepared from brown adipo se tissue of control and cold-exposed hamsters were determined by quan titative immunoblotting and competitive ELISA. Prolonged (four weeks) exposure of hamsters to cold decreased significantly the total content of the a subunits of the stimulatory (G(s alpha)) as well as inhibito ry (G(i alpha(1,2))) G proteins. Interestingly, the reduction in the G (s alpha) content was solely due to a large reduction in the content o f the short (45 kDa) isoform of G(s alpha), while the level of the lon g (52 kDa) isoform of G(s alpha) remained unchanged. The level of the beta subunit of G protein was decreased comparably to the reduction in the total content of the alpha subunits. Cold-induced alterations in the G protein network associated with plasma membranes of brown adipos e tissue were accompanied by changed characteristics of AlF4-sensitive adenylyl cyclase activity.