Biomedical subjects

B J De Santis

Publications and source records attributed to B J De Santis.

5 recordsLinked to original sources

PubMed1996

Nucleotide receptor-mediated decrease of tight-junctional permeability in cultured human cervical epithelium.

Extracellular ATP changes the transepithelial electrical conductance (GT) across cultures of human cervical cells acutely, in a biphasic manner that is characterized by a rapid increase (phase I) followed by a sustained decrease in GT (phase II). We tested the hypothesis that the phase II response is mediated by decreases in the permeability of tight junctions. We studied the effect of ATP on the relative mobilities of Cl- vs. Na+ (uCl/uNa) as calculated from changes in the dilution potential (Vdil). Vdil was induced by lowering NaCl from 130 to 10 mM in either the luminal or subluminal solutions bathing filters containing cells. uCl/uNa was 1.27 across cervical cultures and 1.34 across blank filters, compared with a level of 1.52 in free solution. Increases in GT induced by transepithelial hydrostatic or hypertonic gradients (which increase permeability of lateral intercellular space) had no effect on uCl/uNa. Increases in GT induced by lowering extracellular Ca2+ to < 0.1 mM increased uCl/uNa to levels obtained in blank filters, indicating abrogation of tight-junctional resistance. Phase I response and ionomycin (which produces a sustained phase I-like increase in GT) had no effect on uCl/uNa. The phase II response, however, decreased uCl/uNa from 1.27 to 1.24, and the effect could be abrogated by lowering extracellular Ca2+. These results indicate that phase II decreases in GT across cultured human cervical epithelium are mediated by acute decreases in tight-junctional permeability.

Adenosine Triphosphate↗

PubMed1995

Biphasic regulation of paracellular permeability in human cervical cells by two distinct nucleotide receptors.

The effects of extracellular ATP (ATPe) were characterized in human cervical cells grown on filters. ATPe changed the transepithelial conductance (GT) in a biphasic manner with an initial acute increase of 13 +/- 3% (phase I), lasting approximately 2 min, followed by a sustained decrease of 49 +/- 17% (phase II). ATPe also effected decreases of permeabilities to pyranine and to sucrose, which correspond to the phase II decrease in GT. Both phase I and II effects appear to be mediated by apical nucleotide receptors. However, the phase I effect differed from the phase II effect as follows: 1) a higher 50% effective concentration for ATPe, 22 vs. 3 microM; 2) different nucleotide specificity; 3) lack of influence of pretreatment with pertussis toxin; 4) independence from time in culture after seeding; and 5) involvement of cytosolic calcium, rather than diacylglycerol, as intracellular messenger. These differences suggest the presence of two different types of nucleotide receptors that use different intracellular signaling systems and have opposite effects on the paracellular permeability and electrical conductance. These results suggest that ATPe could regulate cervical mucus production in vivo by regulating the paracellular permeability. Depending on the specific receptors present, ATPe could either increase or decrease mucus production.

Adenosine Triphosphate↗

PubMed1995

Osmolar changes regulate the paracellular permeability of cultured human cervical epithelium.

Extracellular nucleotides induce a biphasic change in the transepithelial electrical conductance (GT) of human cervical cells grown on filters: a rapid increase (phase I) followed by a sustained decrease (phase II). To probe the involvement of the intercellular space, its magnitude was varied by manipulating cell volume through changes in extracellular osmolarity. Under baseline conditions [GT = 115 mS/cm2 (approximately 9 omega.cm2)] and during phase II, hypertonic challenges resulted in an increase in GT (0.98% .mosmol-1.l-1 and 0.73%.mosmol-1.l-1, respectively). However, a hypertonic challenge during phase I decreased GT (-0.16%.mosmol-1.l-1). Hypotonic challenges decreased GT during baseline, phase I, and phase II conditions by -1%.mosmol-1.l-1. Similar trends were observed with regard to pyranine permeability. Reduction of extracellular calcium increased GT, abrogated the phase II effect of extracellular ATP, and reversed the effect of a hypertonic challenge. The additive nature of the permeability changes in response to osmotic challenges and to ATP during phase II suggests that different sites are involved in each response, i.e., the resistance of the intercellular space changes with osmolarity and that of the tight junction during phase II.

Adenosine Triphosphate↗

PubMed1994

ATP decreases acutely and reversibly transport through the paracellular pathway in human cervical cells.

We studied the effect of ATP on transepithelial transport through the paracellular pathway in human cervical cells. Transepithelial conductance and transepithelial permeability (determined from the measurements of unidirectional flux of inert molecules) were measured in Caski cells grown on permeable support. Transepithelial conductance was 55.9 +/- 17.7 mS/cm2 and permeability was 12.5 +/- 2.7 x 10(-6) cm/s for a 0.51-kDa probe. Addition of ATP to the medium decreased acutely and reversibly the conductance and the permeability to probes between 0.18 and 10 kDa by 23-31% in a dose-related fashion; the 50% effective concentration was 1 microM, with a maximal effect at 5-10 microM extracellular ATP. The ATP effect was observed regardless of the pressure gradient across the epithelium. These results indicate that extracellular ATP in micromolar concentrations decreases acutely and reversibly the permeability through the paracellular pathway in cervical cells, possibly by affecting the permeability of the tight junctions and the resistance of the intercellular space. On the basis of these data, we speculate that ATP may play a role in the regulation of solutes and fluid transport across the cervical epithelium in vivo.

Adenosine Triphosphate↗

PubMedDate not supplied

Characterization of paracellular permeability in cultured human cervical epithelium: regulation by extracellular adenosine triphosphate.

OBJECTIVE: The purpose of the present study was to compare the permeability and regulation of paracellular transport in human cervical cells with those in epithelial cells of other organs. METHODS: Cervical cells (ECE16-1, Caski, and HT3) were grown on filters, and transepithelial electrical conductance (GT) and the permeability to pyranine (PPyr) were determined. RESULTS: Cervical cultures were characterized by high GT (83-125 mS.cm-2) and high PPyr (6.2-18 x 10(-6).sec-1). The GT was not significantly affected by cell density but was increased by 20% by lowering extracellular calcium to 0.45 mmol/L or less. The high values of GT and PPyr and the regulation by extracellular calcium indicate that all three cervical cell lines have "leaky" tight junctional complexes. Addition of extracellular adenosine triphosphate (ATP) at 50 mumol/L to the cervical cultures evoked a biphasic change in GT that was unique to the cervical cells: an initial increase, followed by a sustained decrease by 30% from baseline GT. The decrease of GT was associated with a decrease in PPyr by 17%, indicating that ATP had an effect on the tight junctional/paracellular permeability. The ATP effect was reversible either by washing or by chemical hydrolysis with ATPase. The non-cervical cell lines all responded to extracellular ATP with a transient increase in GT, but not with the pronounced decrease. CONCLUSION: The permeability of the paracellular pathway can be regulated in cervical epithelia by mechanisms that may be different from those in epithelial cells from other organs.

Adenosine Triphosphate↗