Bradykinin has effects on renal electrolyte metabolism. It reportedly alters blood flow, affects renal vasculature and directly influences the transporting epithelia (Kauker, 1980). It has been reported that guinea pig tissues possess high affinity binding sites for bradykinin and the present study compares renal binding sites for bradykinin from rat and guinea pig by ligand binding and autoradiography.Crude brush border basolateral membranes were prepared by the method of Heidrich et al (1972). were incubated in 25 mM TES buffer, pH 6.8, containing 1 mM 1,10 phenanthroline, 1 mM dithiothreitol, 0.1 mM bacitracin, 5 vM SQ 20881 and 0.2% BSA with [3H]-bradykinin in a total volume of 500 il for 1 hour at 40C. Non-specific binding was determined by the inclusion of 10 vM bradykinin. The reaction was terminated by filtration through Whatman GF/B filters and bound radioactivity determined by liquid scintillation spectrometry. Autoradiography was carried out on 10 Vm slices mounted onto gelatin-coated glass slides. As far as possible incubation conditions were kept similar to those determined for membrane binding, ligand concentrations used were 0.5,1,20 nM, non-specific binding was determined using 10 vM unlabelled bradykinin and the incubation time was 90 min at 40C. The slides were apposed to LKB ultrafilm for 6-8 weeks and analysed on a Quantimet densitometer.High affinity saturable binding sites were detected in guinea-pig cortex membranes, the Kd was 125+23 pM and the Bmax 2.6 + 0.27 pmol/mg protein. The In the brain iron is unevenly distributed with highest concentration being present in globus pallidus, substantia nigra, putament and caudate nucleus (Youdim, 1985). Iron-deficiency (ID) in rats causes a selective subsensitivity of dopamine D2 receptor as indicated by the reduced 3H-spiperone binding Bmax in the caudate nucleus and diminished apomorphine induced behaviours (Ashkenazi et al., 1982). Furthermore, iron chelators o-phenanthroline and desferrioxamine inhibit the binding of 3H-spiperone (Ben-Shachar et al., 1985). In the present study we have systematically examined the effect of ID on serum iron, brain non-haem iron, 3H-spiperone binding in caudate nucleus and behavioural response to apomorphine as well as the influence of iron-supplementation in iron-deficient rats.Male Sprague-Dawley rats (21 days old) were fed an iron-deficient diet for 4 weeks (Ben-Shachar et al., 1985). Determination of the above parameters at weekly intervals showed that by the fourth week there were reductions in serum iron (78%, P<0.001), brain non-haem iron (37%, P<0.0l), 3H-spiperone binding (41l, P<0.01) and apomorphine (2mg/kg) behavioural response (52%, P<0.001). These could all be reversed by supplementation of the iron-deficient diet with ferrous sulphate (200 ppm) for up to 2 weeks. Since the effect of ID on dopamine D2 receptor cannot be reversed in vitro by the addition of ferric or ferrous sulphate (10-3M), the results indicated the possible inv9lvement of iron in DA D2 receptor protein synthesis. In vivo in...
