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The sex hormone binding globulin (SHBG) capacity was measured by ammonium sulfate precipitation in the plasma of women using various progestational steroids and combined hormonal contraceptives. For reference purposes, determinations were done in the plasma of normal males, normal menstruating women, women at different stages of pregnancy, post-menopausal women, 0.050 mg daily. and women using ethinylestradiol (EE%)The progestational compounds, d-norgestrel (0.030 mg daily), lynestrenol (0.5 mg daily), and medroxyprogesterone acetate (150 mg three-monthly intramuscularly), caused a decrease of about 30% below the level found in normal menstruating women. With lynestrenol 5 mg daily, a further decrease of SHBG was observed. EE (0.050 mg daily) alone increased SHBG. This effect of EE2 was (part y) 1 neutralized by its combination with d-norgestrel or lynestrenol. The combination of EE2 with megestrol acetate gave rise to high SHBG capacity values, comparable to those attained during pregnancy.The response of SHBG to the use of hormonal contraceptives is different from that of transcortin-binding capacity as found by other authors.

1The binding of the first selective radiolabelled histamine H3-receptor 6 Competition binding curves of H3-agonists were biphasic and showed a rightward shift upon the addition of the nonhydrolysable GTP analogue, guanosine 5'-o-(3-thio) triphosphate (GTPTyS; 100 pLM) which implicates the interaction of histamine H3-receptors with G-proteins. The affinities of the H3-receptor antagonists iodophenpropit, thioperamide and burimamide were not altered by GTPyS. 7 Histamine competition binding curves were shifted to the right by different nucleotides (100 tiM) with a rank order of potency GTPyS>Gpp(NH)p, GTP. 8 In vitro autoradiographic studies revealed a heterogeneous distribution of ['251]-iodophenpropit binding sites in rat brain, with highest densities observed in specific cerebral cortical areas and layers, the caudate-putamen complex, the olfactory tubercles, the hippocampal formation, the amygdala complex, the hypothalamic area and the mammillary bodies. 9 It is concluded that the histamine H3-receptor antagonist, ['251I]-iodophenpropit, meets the criteria for a suitable radioligand for histamine H3-receptor binding studies in rat brain.

The peroxidation of lipids in biological membranes is a destructive phenomenon that can he elicited in various ways. Surface receptor molecules that allow ceffs to respond to hormones are possibly inactivated during lipid peroxidation. Effects of lipid peroxidation on receptors have not been extensively examined thus far. This investigation shows that there is a decrease in fi-adrenoceptor density (measured as specific ( -)-(125i]iodocyanopindoloi binding) during lipid peroxidation, in both lungs and erythrocytes of the rat. To this end, lung membranes (containing both /I,-and b,-adrenoeeptors) and intact erythrocytes (containing a homogeneous /3,-adrenoceptor population) were pretreated with cumene hydroperoxide (lung membranes with 0.1 mM and erythrocytes with 1 mM) and Fez+ (1 x 10e5 M) for 40 min which resulted in extensive lipid peroxidation measured as malondialdehyde formation. The ratio fl,-:/I,-adrenoceptor density in lung membranes after treatment with cumene hydroperoxide did not change and remained at 305~70%. A single injection (i.p.) with the herbicide paraquat (50 mg/kg, 24 h), which is known to cause Lung damage via lipid peroxidation, resuhed in similar alterations in receptor density to those caused by cumene hydroperoxide in the in vitro experiments.

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