The function of the nephron, the anatomical unit of the kidney, is segmented; at least 12 segments have been identified that differ in their morphology, transport properties and hormonal responsiveness. The medullary portion of the thick ascending limb of the loop of Henle (mTALH) has one of the highest concentrations of (Na+ + K+)ATPase found in mammalian tissues, reflecting the importance of this nephron segment in the regulation of extracellular fluid volume, as active sodium transport is driven by (Na+ + K+)ATPase. Here, in cells derived primarily from the mTALH of the outer medulla of rabbit kidney, we have identified a cytochrome P450-dependent monooxygenase system which metabolizes arachidonic acid to two biologically active oxygenated products; one of the products inhibits (Na+ + K+)ATPase and the other relaxes blood vessels. We report that formation of these oxygenated arachidonate metabolites is stimulated by arginine vasopressin (AVP) and salmon calcitonin (SCT).

SUMMARY We studied the effects of anteroventral third ventricle (AV3V) lesions on the vascular Na + -pump activity of deoxycorticosterone acetate-salt (DOCA-salt) treated rats. Blood pressures and Na + -pump activity of the isolated tail arteries, measured as ouabain-sensitive w Rb + -uptake, were determined in untreated control rats, DOCA-salt treated rats, rats with AV3V lesions, and rats with AV3V lesions which were treated with DOCA-salt. Control rats receiving DOCA treatment developed higher blood pressures than rats receiving no DOCA treatment. Placement of AV3V lesions prior to administration of DOCA prevented the increase in blood pressure. Vascular Na + -pump activity in the DOCA-treated group was reduced by 20% compared to all other groups. The AV3V lesions prevented the suppression of Na + -pump activity caused by DOCA treatment. Suppression of vascular Na + -pump activity was due to a humoral substance since Na + -punip activity of tail arteries from control rats incubated in plasma from DOCA-salt treated rats was suppressed by 25% when compared to those incubated in control plasma. Our findings support the hypothesis that a circulating pressor substance is at least partially responsible for the development of DOCA-salt hypertension and that the mechanism by which AV3V lesions prevent DOCA hypertension may be through the interruption of secretion, transport, or synthesis of this factor. (Hypertension 4: 575-580, 1982) KKV WORDS • hypertension • blood pressure • Na + -pump activity • Rb-uptake • tail artery • AV3V lesion

Stretch is known to stimulate myometrial hyperplasia and hypertrophy in early pregnancy and uterine contraction at term. We propose that transduction of the stretch signal involves alteration of intracellular calcium signalling, including changes in transient receptor potential canonical (TRPC) isoform expression. The aim of the present study was to investigate the effect of prolonged mechanical (tonic) stretch in vitro on human myometrial smooth muscle cell calcium signalling and TRPC expression. Cells were cultured from myometrial biopsies, obtained from women undergoing elective Caesarean section at term, grown on Flexiplates and subjected to 25% tonic mechanical stretch for 1, 4 and 14 h. Time-matched control cells were not stretched. Mechanical stretch (14 h) increased basal calcium entry and cyclopiazonic acid (CPA)-induced calcium/Mn(2+) entry (P < 0.05) in Fura-2 loaded cells. The calcium selectivity of CPA-thapsigarin induced inward currents, measured by patch clamp electrophysiology, was also increased in stretched cells compared with control cells (P < 0.05). Real time PCR and Western blot data demonstrated that TRPC3 and TRPC4 mRNA and TRPC3 protein expression were increased by stretch (P < 0.05), respectively. These data support the hypothesis that uterine stretch modulates uterine growth and contractility in pregnancy via alterations in calcium signalling.

IntroductionThe putative mannose receptor (MR), previously implicated in mannosyl-rich glycoprotein-induced mitogenesis in bovine airway smooth muscle (ASM) cells, was studied to determine its properties. (7). The mitogenic effect is blocked by yeast mannan, a mannose receptor (MR) blocker (8), but not by mannose-6-phosphate, a specific blocker of the cation independent mannose-6-phosphate/insulin-like growth factor II receptor (9), suggesting the involvement of a mannose-recognizing moiety (7).The well-studied mannose receptor of macrophages (M0MR) is involved in receptor-mediated endocytosis and molecular scavenging of ManGP as well as phagocytosis and host defense against mannosyl-rich pathogens (10-12). Mannosylrich enzymes such as lysosomal hydrolases including Hex (11), myeloperoxidase (13), and plasminogen activator (14)

SUMMARY Cells were isolated from the outer medulla of the rabbit kidney, primarily from the thick ascending limb of Henle's loop (mTALH). These mTALH cells are heavily invested with a cytochrome P450-Iinked monooxygenase that represents the third pathway by which arachidonic acid is metabolized. After cell separation, approximately 80% of the cells proved to be mTALH in origin, based on electron microscopic criteria and immunofluorescent localization of Tamm-Horsfall protein, a specific marker for mTALH cells. The specific activity of alkaline phosphatase, a marker for proximal tubular cells, decreased threefold after separation of mTALH cells from outer medullary cells, associated with a fourfold Increase in the capacity of the separated mTALH cells to metabolize arachidonic acid. Incubation of mTALH cells with C-arachidonic acid resulted in formation of oxygenated metabolites, identified as two peaks (P t and P 2 ), which accounted for 30 to 40% of the recovered radioactivity. Formation of prostaglandin E 2 and F^, accounted for only 3 to 5%. The chromatographic retention times of Pi and P 2 were different from products of lipoxygenases. An inhibitor of cytochrome P450-dependent enzymes, SKF-525A (50 fj.M), reduced product formation by mTALH cells by more than 70%, while induction of cytochrome P450 increased product formation. Formation of P, and P 2 by cell-free homogenates of mTALH was totally dependent on the presence of nicotinamide adenine dinucleotide phosphate, reduced form (NADPH), which suggests a NADPHdependent cytochrome P450-linked monooxygenase pathway. Vasopressin and calcitonin (10" l0 M to 10~7 M) stimulated release of arachidonic acid metabolites from mTALH cells. P 2 yielded a principal product that proved to be a potent inhibitor of Na,K-ATPase, whereas the major component of P, was a weak inhibitor. The latter material relaxed isolated blood vessels. In mTALH cells obtained from rabbits made hypertensive by aortic constriction, increased P, and P 2 formation could be demonstrated within 7 days.