EXPRESSION OF SULFONYLUREA RECEPTORS IN BOVINE MONOCYTES FROM ANIMALSWITH A DIFFERENT METABOLIC-RATE

The aim of this study was to investigate the relationship between expr ession of sulphonylurea receptors (SUR) and metabolic rate (MR). SUR o n monocytes and cells from muscle tissue were detected using fluoresce nt glibenclamide and flow cytometry. Transmembrane potential differenc es were detected by oxonol dye fluorescence measurements. A bovine mod el was used to induce differences in the MR by exposure to different a mbient temperatures (4 degrees C and 18 degrees C), by different feedi ng levels (1.0- and 1.6-fold the metabolizable energy requirement for maintenance) and by alpha(2)-adrenergic stimulation. We found that cel ls from skeletal muscle (m. semimembranosus), immunochemically identif ied as smooth muscle cells, skeletal muscle fibres and monocytes, resp onded in comparable fashions to glibenclamide and ATP, i.e. with a dep olarization, and to cromakalim with a polarization, suggesting that mo nocytes are useful indicators of regulatory events occurring in muscle cells. Glibenclamide fluorescence was assumed to represent SUR associ ated with K-ATP channels. Significant differences were detected in the percentage of depolarized monocytes in the different variants of the model. A linear correlation between monocytes that bound fluorescent g libenclamide and the MR was evident (with a coefficient of determinati on of 0.94) and was reproducible following reduction of the MR, by alp ha(2)-adrenergic stimulation, suggesting that expression is involved i n the regulation of whole-body energy expenditure.