ABSTRACT
This experiment was undertaken to evaluate the effect of D3 [dopamine receptor] activation by intravenous infusion [iv] of 7-OH-DPA T [as specific D3 receptor agonist] on the structural and functional activity of the kidney and adrenal gland and to evaluate the possible mechanism[s] of its action. This study was carried out on 36 adult male Balady rabbits weighing 1.2-1.5 kg body weight. Animals were divided into four groups, one as a control and three groups were used to assess the effect of iv infusion of 7-OH-DPAT at a rate of 0.01, 0.05, 0.1 ug/kg/min for 120 mm. Rabbits were randomly assigned into renal and adrenal assessments. This experiment revealed that activation of D3 receptors, especially with the high dose, was associated with marked dilatation of glomerular blood capillaries and blood vessels among tubules, Structural changes in the juxta glomerular apparatus with signs of degeneration in the macula densa cells were observed. Reduction and distortion of the brush border of the proximal convoluted tubules [PCT,] was noticed. Ultrastructural changes were characterized by dispersion of the ribosomes, numerous cytoplasmic vacuoles, chromatin condensation, and presence of cytoplasmic inclusion bodies. Alteration in the size and morphology of mitochondria, associated with widening of the basal enfoldings were observed, Physiological assessment revealed dose dependent increase glomerular filtration rate, a significant increase in mean levels of urine flow rate, Na excretion rate and K excretion rate. Also, significant decrease in the angiotensin-converting enzyme activity was observed in this work. This study also, revealed involvement of the cells of the adrenal cortex and medulla with variable degrees of degenerative changes, including congestion of the blood capillaries and disarrangement of the zona glomerulosa cells which were occupied with darkly stained cytoplasmic granules. Decreased activity of the zona glomerulosa, was manifested by decrease in aldosteroene secretion, decrease in serum sodium and increase Na excretion rate