Biomedical subjects

C Y Yip

Publications and source records attributed to C Y Yip.

4 recordsLinked to original sources

PubMed2003

Multiple purinergic receptors lead to intracellular calcium increases in cultured rat Sertoli cells.

Our previous study has demonstrated the activation of calcium-dependent Cl(-) secretion through P2Y(2) receptors by extracellular nucleotides. To evaluate the contribution and involvement of other receptor subtypes to this physiological response, the purpose of this study was to investigate the regulation of intracellular calcium concentration ([Ca(2+)](i)) by different purinergic agonists in cultured rat Sertoli cells. Cultured epithelia of Sertoli cells from immature rats were grown on glass coverslips and the purity was confirmed by immunohistochemistry. Intracellular calcium concentration was monitored by microspectrofluorimetric technique using calcium sensitive fluorescent dye Fura-2. Results showed that UTP and ATP consistently increased [Ca(2+)](i). Adenosine, AMP and 2-methylthio-ADP (2-MeSADP) failed to elicit a discernible response. Cross desensitization experiments suggested that the responses to UTP and ATP were mediated by a common receptor population. This is consistent with the presence of receptors belonging to the P2Y(2) subclass. Sertoli cells also responded to 2-methylthio-ATP (2-MeSATP) and ADP but not 2-methylthio-ADP (2-MeSADP) in a concentration-dependent manner. Moreover, the ATP-or UTP-pretreated epithelia continued to respond to ADP, indicating that these cells express at least one additional receptor population that allowed nucleotides to increase [Ca(2+)](i). Apart from the P2Y receptor agonists, the P2X(4) and P2X(7) agonist, 2' and 3'-O-(4-benzoylbenzoyl)-ATP (Bz-ATP), also evoked [Ca(2+)](i) increases in rat Sertoli cells. Messenger RNA transcript corresponding to P2Y(1), P2Y(2), P2X(4) and P2X(7) receptors genes were detected using RT-PCR. Taken together, these data indicate that both metabotropic receptors and ionotropic receptors are present in rat Sertoli cells through which extracellular nucleotides can act.

Adenosine Diphosphate↗

PubMed2002

Involvement of Na+-HCO3- cotransporter in mediating cyclic adenosine 3',5'-monophosphate-dependent HCO3- secretion by mouse endometrial epithelium.

The present study investigated the involvement of Na+-HCO3- cotransporter in mediating cAMP-stimulated HCO3- secretion across the cultured mouse endometrial epithelium using the short-circuit current (I(SC)) technique and intracellular pH measurement. Forskolin stimulated a rise in the I(SC), 55.6% and 52.1% of which could be reduced by the removal of extracellular Cl- or by eliminating the contribution of Cl- secretion by bumetanide, an inhibitor of Na+-K+-2Cl- cotransporter, respectively. More than 80% reduction in the forskolin-induced I(SC) was obtained when both Cl- and HCO3- in the bath were removed or in HCO3--free solution with bumetanide, indicating that the I(SC) depended on both Cl- and HCO3-. The presence of the Na+ channel-blocker amiloride in the apical solution did not reduce the forskolin-induced I(SC); however, the I(SC) could be abolished by removing Na+ from the bathing solution, suggesting that the Cl-- and HCO3--dependent I(SC) was also dependent on basolateral Na+. The forskolin-stimulated I(SC) could be reduced 43.6% by removal of HCO3- and 47.9% by a Na+-HCO3--cotransporter inhibitor, dihydrogen-4,4'-didsothiocyanostilbene-2,2'-disulfonic acid (H2DIDS). The inhibitory effect of H2DIDS was observed in Cl--free solution, but not when HCO3- was removed, thus confirming its effect on HCO3--dependent transport. Intracellular pH measurements demonstrated that the recovery from cellular acidification depended on the presence of both basolateral Na+ and HCO3-, further indicating the involvement of Na+-HCO3- cotransporter. Reverse transcription-polymerase chain reaction experiments confirmed the expression of Na+-HCO3- cotransporter in the mouse endometrium. The results suggest that basolaterally located Na+-HCO3- cotransporter is involved in mediating cAMP-stimulated HCO3- secretion across the mouse endometrial epithelium.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗

PubMed2000

Multiple P2Y receptor subtypes in the apical membranes of polarized epithelial cells.

Apical ATP, ATP, UTP and UDP evoked transient increases in short circuit current (I(SC), a direct measure of transepithelial ion transport) in confluent Caco-2 cells grown on permeable supports. These responses were mediated by a population of at least three pharmacologically distinct receptors. Experiments using cells grown on glass coverslips showed that ATP and UTP consistently increased intracellular free calcium ([Ca(2+)](i)) whilst sensitivity to UDP was variable. Cross desensitization experiments suggested that the responses to UTP and ATP were mediated by a common receptor population. Messenger RNA transcripts corresponding to the P2Y(2), P2Y(4) and P2Y(6) receptors genes were detected in cells grown on Transwell membranes by the reverse transcriptase - polymerase chain reaction. Identical results were obtained for cells grown on glass. Experiments in which I(SC) and [Ca(2+)](i) were monitored simultaneously in cells on Transwell membranes, confirmed that apical ATP and UTP increased both parameters and showed that the UDP-evoked increase in I(SC) was accompanied by a [Ca(2+)](i)-signal. Ionomycin consistently increased [Ca(2+)](i) in such polarized cells but caused no discernible change in I(SC). However, subsequent application of apical ATP or UTP evoked a small rise in I(SC) but no rise in [Ca(2+)](i). UDP evoked no such response. As well as evoking increases in [Ca(2+)](i), the ATP/UTP-sensitive receptors present in Caco-2 cells thus allow direct control over ion channels in the apical membrane. The UDP-sensitive receptors, however, appear to simply evoke a rise in [Ca(2+)](i).

Adenosine Triphosphate↗

PubMed1991

Simultaneous multiple site arteriolar vasomotion measurement using digital image analysis.

An automatic digital image processing technique for simultaneous vasomotion analysis in peripheral microcirculation at multiple sites and in real time is presented. The algorithm utilizes either fluorescent or bright field micro-images of the vasculature as input. The video images are digitized and analyzed on-line by an IBM RT PC, using digital filtering and edge detection. The sampling frequency is higher than 5 Hz when only one site is tracked and decreases as the number of sites is incremented. Performance of the algorithm was tested for a hamster cutaneous microcirculation model.

Algorithms↗