We have studied the mechanism of the regulation of plasma membrane Ca2+ permeability by the degree of filling of the intracellular Ca2+ stores. Using Mn2+ as a Ca2+ surrogate for plasma membrane Ca2+ channels, we found that Mn2+ uptake by rat thymocytes is inversely related to the degree of filling of the intracellular Ca2+ stores. This store-dependent plasma membrane permeability is inhibited ...

omega-Hydroxylation of leukotriene B4 (LTB4) has been reported in human and rodent polymorphonuclear leukocytes; preliminary information indicates that this metabolism is cytochrome P-450 dependent. Therefore, these studies were initiated to characterize the cytochrome P-450-dependent metabolism of LTB4 in other tissues. LTB4 was metabolized by rat hepatic microsomes to two products, 20-hydroxy...

Liver microsomes contain a mixed function oxidase system capable of metabolizing a broad range of biologically active substances, including drugs, steroids, and environmental chemicals such as polycyclic hydrocarbons. Certain hemoproteins, collectively referred to as cytochrome P-450, function as the terminal oxidase in this system. The fact that this hepatic mixed function oxidase system is se...

Good, David W., Thampi George, and Donna H. Wang. Angiotensin II inhibits HCO3 2 absorption via a cytochrome P-450-dependent pathway in MTAL. Am. J. Physiol. 276 (Renal Physiol. 45): F726–F736, 1999.—The role of ANG II in the regulation of ion reabsorption by the renal thick ascending limb is poorly understood. Here, we demonstrate that ANG II (1028 M in the bath) inhibits HCO3 2 absorption by ...

The role of cytochrome P-450 in the myogenic response of isolated, perfused renal arcuate arteries of dogs to elevations in transmural pressure was examined. The phospholipase A2 inhibitor oleyloxyethylphosphorylcholine (1 and 10 ,uM) inhibited the greater than threefold increase in active wall tension in these arteries after an elevation in perfusion pressure from 80 to 160 mm Hg. Inhibition o...

Highly purified liver microsomal cytochrome P-450 catalyzes the hydroperoxide-dependent hydroxylation of a variety of substrates in the absence of NADPH, NADPHcytochrome P-450 reductase, and molecular oxygen. The addition of phosphatidylcholine is necessary for maximal activity. The absence of flavoproteins and cytochrome b, from the cytochromeP-450 preparations rules out the involvement of oth...

An antibody preparation to purified, homogeneous TPNHcytochrome c reductase from pig liver microsomes was shown to inhibit concomitantly TPNH-cytochrome c reductase (NADPH-cytochrome c oxidoreductase, EC 1.6.2.3) and ethyhnorphine N-demethylase activities in pig liver microsomes. The antibody also inhibited TPNH-cytochrome c reductase and TPNH-cytochrome P-450 reductase activities in rat and pi...

Exposure to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) causes loss of dopaminergic neurons in humans, primates and mice. Exposure of sagittal slices of mouse brain to MPTP (100 pM) caused inhibition of mitochondrial NADH-dehydrogenase activity. Leakage of lactate dehydrogenase from the slice into the medium was observed following incubation of slices with 1 nM MPTP. Neurotoxicity induc...

Aromatase is the key enzyme in the synthesis of estrogens and mediates the conversion of androstenedione and testosterone to estrone and estradiol. Because of the importance of estrogen in stimulating breast cancers, the inhibition of estrogen synthesis is a logical approach to treatment. Aromatase is an excellent target for inhibition, because it is the last step in steroid biosynthesis, and, ...