Abstract
Adenylate cyclase (AC) activity was studied in the choroid plexus and brain vessels of rat and mouse using a recently improved cytochemical method (Palkama A, Kaufman HE, Uusitalo R, Uusitalo H, Virtanen J, Huhtaniitty S: J Histochem Cytochem 29:898, 1981). For comparison, the vasculature of skeletal muscle was also examined. Specimens were fixed for 5 min in 1% paraformaldehyde or 1% paraformaldehyde and 0.1% glutaraldehyde supplemented with activators of AC: isoproterenol and 5'-guanylylimidodiphosphate or forskolin. These activators were also present in the "activating solution" and in the incubation medium. For control purposes no activators were used. Various capturing agents were introduced into incubation media: SrCl2, Pb citrate, NdCl3, and CeCl3. Satisfactory results were obtained with both fixatives, both activators, and the capturing agents SrCl2 and Pb citrate. In rat choroid plexus AC activity was localized in the basal and lateral plasmalemma of epithelial cells, in the plasmalemma of cells interposed between epithelium and capillaries and occasionally in pinocytotic vesicles of endothelial cells. In micro-blood vessels of rat brain, the reaction appeared in the luminal or in both luminal and abluminal plasmalemma of endothelial cells and in smooth muscle cells. In skeletal muscle microvessels, reaction product was mainly located in numerous pits and pinocytotic vesicles associated with luminal plasmalemma of endothelial cells. Some reaction in rat cortex was occasionally observed in Golgi saccules of neurons and in postsynaptic densities. In the mouse choroid plexus and brain vessels the reaction was notably less intense, suggesting the existence of species differences in AC activity as revealed by cytochemical technique.