AVP-stimulated nucleotide secretion in perfused mouse medullary thick ascending limb and cortical collecting duct

Extracellular nucleotides are local, short-lived signaling molecules that inhibit renal tubular transport via both luminal and basolateral P2 receptors (1, 2). Apparently, the renal epithelium itself is able to release nucleotides (3, 4). The mechanism and circumstances under which epithelia nucleotide release is stimulated remains elusive (5, 6). Here, we investigate the phenomenon of nucleotide secretion in intact perfused mouse medullary thick ascending limb (mTAL) and cortical collecting duct (CCD). The nucleotide secretion was monitored by a biosensor cell placed to register nucleotides in the tubular out-flow. [Ca2+]i was measured simultaneously in the biosensor cells and the renal tubule with fluo-4. We were able to identify spontaneous tubular nucleotide secretion in resting perfused mTAL. This was seen as lively [Ca2+]i oscillations in the nucleotide biosensor cells when the tubular outflow fluid engulfed the sensing cells. In mouse mTAL 10 nM AVP and dDAVP induced robust [Ca2+]i oscillations, whereas AVP in the CCD induced large, slow and transient [Ca2+]i elevations. Importantly, we identify that AVP/ dDAVP triggers tubular secretion of nucleotides in mTAL. After addition of AVP/dDAVP the biosensor cells registered bursts of nucleotides originating from the tubular perfusate. The approximated tubular nucleotide concentration reached peak values of ～0.2-0.3μM. A very similar response was observed after AVP stimulation of CCDs. Thus, AVP stimulated tubular secretion of nucleotides in a burst like pattern with peak tubular nucleotide concentrations in the low micromolar range. Luminal nucleotides are prone to activate luminal P2 receptors (1) which in turn are well described to inhibit AVP-augmented aquaporin-2-dependent water absorption (7) or ENaC-mediated Na+ transport (8). Therefore, we speculate that local nucleotide signaling is an intrinsic feed-back element of hormonal control of renal tubular transport (9)

Arch Sex Behav

Thirty years after the beginning of the HIV epidemic, gay, bisexual, and other men who have sex with men (collectively called MSM) bear a disproportionate burden of HIV in the United States and continue to acquire a distressingly high number and proportion of new infections. Historically, HIV prevention for MSM has been focused on individual-level behavior change, rarely intervening with MSM as part of a couple. Yet, an estimated 33\u201367% of HIV infections among MSM are acquired from primary sexual partners, suggesting that work with MSM as couples could be an important contributor to prevention. Given the emergence of high impact combination HIV prevention, it is timely to consider how work with the broad variety of male couples can improve both personal and community health. Couples HIV testing and counseling for MSM is an important advance for identifying men who are unaware that they are HIV-positive, identifying HIV-discordant couples, and supporting men who want to learn their HIV status with their partner. Once men know their HIV status, new advances in biomedical prevention, which can dramatically reduce risk of HIV transmission or acquisition, allow men to make prevention decisions that can protect themselves and their partners. This paper highlights the present-day challenges and benefits of using a couples-based approach with MSM in the era of combination prevention to increase knowledge of HIV status, increase identification of HIV discordant couples to improve targeting prevention services,and support mutual disclosure of HIV status.CC999999/Intramural CDC HHS/United States2017-01-09T00:00:00Z24233328PMC5221480vault:2090

P2Y2 receptor knock-out mice display normal NaCl absorption in medullary thick ascending limb

Local purinergic signals modulate renal tubular transport. Acute activation of renal epithelial P2 receptors causes inhibition of epithelial transport and thus, should favor increased water and salt excretion by the kidney. So far only a few studies have addressed the effects of extracellular nucleotides on ion transport in the thick ascending limb. In the medullary thick ascending limb (mTAL), basolateral P2X receptors markedly (~25%) inhibit NaCl absorption. Although this segment does express both apical and basolateral P2Y2 receptors, acute activation of the basolateral P2Y2 receptors had no apparent effect on transepithelial ion transport. Here we studied, if the absence of the P2Y2 receptor causes chronic alterations in mTAL NaCl absorption by comparing basal and AVP-stimulated transepithelial transport rates. We used perfused mouse mTALs to electrically measure NaCl absorption in juvenile (35 days) male mice. Using microelectrodes, we determined the transepithelial voltage (Vte) and the transepithelial resistance (Rte) and thus, transepithelial NaCl absorption (equivalent short circuit current, I’sc).We find that mTALs from adult wild type (WT) mice have significantly lower NaCl absorption rates when compared to mTALs from juvenile WT mice. This could be attributed to significantly higher Rte values in mTALs from adult WT mice. This pattern was not observed in mTALs from P2Y2 receptor knockout (KO) mice. In addition, adult P2Y2 receptor KO mTALs have significantly lower Vte values compared to the juvenile. No difference in absolute I´sc was observed when comparing mTALs from WT and KO mice. AVP stimulated the mTALs to similar increases of NaCl absorption irrespective of the absence of the P2Y2 receptor. No difference was observed in the medullary expression level of NKCC2 in between the genotypes.These data indicate that the lack of P2Y2 receptors does not cause substantial differences in resting and AVP-stimulated NaCl absorption i