Search PubMed⌕ Search

Biomedical subjects

J Poggioli

Publications and source records attributed to J Poggioli.

At least 55 records · Page 3Linked to original sources
PubMed1982

Actions of ionomycin in rat parotid gland.

The effects of ionomycin (SQ 23,377), a carboxylic acid Ca-ionophore, on the rat parotid acinar cell were investigated. Ionomycin stimulated 86Rb efflux from parotid slices and was substantially more potent and efficacious than the Ca-ionophore, A-23187. The release of 86Rb was dependent on the concentration of ionomycin and of Ca. Ionomycin also stimulated 22Na uptake and 3H-protein secretion, but did not stimulate the incorporation of 32PO4 into phosphatidylinositol. These observations are consistent with an action of ionomycin in increasing cytosolic Ca by acting as an ionophore and not involving endogenous receptors. Pretreatment with ionomycin inhibited the transient, Ca-independent responses to carbachol or physalaemin. When ionomycin was added to parotid cells pre-equilibrated with 45Ca, a net loss of radiocalcium was observed. These observations suggest that ionomycin can release the receptor-regulated cellular Ca pool. Morphological studies did not reveal any nonspecific deleterious effects in the cells after incubation with 2.67 microM ionomycin.

Animals↗
PubMed1981

Receptor regulation of calcium release and calcium permeability in parotid gland cells.

The mechanism by which hormones and neurotransmitters regulate fluid secretion in exocrine glands apparently involves the regulation of transmembrane movements of electrolytes, a process for which Ca serves as a second messenger. Analysis of the kinetics of efflux of 86Rb+ (a marker for K+) indicates that the initial phase of the response to secretagogues is mediated through the release of Ca from a cellular pool inaccessible to chelating agents. By investigating the movements of 45Ca under nearly steady-state conditions, we find that this cellular pool can be filled from the extracellular space without a concomitant elevation in ionized intracellular Ca2+. This suggests that the cellular pool is probably associated with the plasma membrane. We have also investigated the possible role of phosphatidic acid in the mechanism by which receptors mobilize Ca2+. Our results suggest that phosphatidic acid, formed on receptor activation, may directly mediate Ca influx into the acinar cell.

Animals↗
PubMed1980

Volume- and temperature-dependent permeabilities in isolated rat liver cells.

1. Water, K, Na and Cl contents and fluxes of K and Na were determined in isolated rat hepatocytes incubated at 1 degrees C (90 min) then at 38 degrees C (60 min). At 1 degrees C cells progressively gained Na and Cl, lost K and increased their volume by 17%. 2. Rewarming triggered a net loss of K and gain of Na. They were transitory (about 60 sec) being overcome rapidly by movements in the opposite direction until cells recovered their initial K and Na gradients. 3. Determination of time courses of the K rate constant (kappa' K) and net Na influx (phi Na) in cells incubated in ouabain K-free media indicated that these paradoxical movements were due to a temporary shunting of the Na pump by sudden increases in K and Na permeabilities. 4. Increases in kappa' K and phi' Na were not sensitive to inhibitors of Ca-activated K channels such as quinine (10(-3) M) of apamin (10(-8) M), suggesting they were not dependent on internal ionized Ca. 5. In control media containing 1.8 mM-Ca divalent ionophore A23187, though stimulating the Ca pump (Ca efflux), presumably by increasing internal ionized Ca concentration, did not cause substantial and rapid changes in K permeability. This supports the hypothesis that Ca-sensitive K channels are lacking in rat hepatocytes. 6. A 10% increase in cell volume provoked by a hypo-osmotic shock triggered increases in both kappa' K and phi' Na with time courses very similar to those brought about by rewarming. 7. It is proposed that transient changes in K and Na permeabilities are the consequence of the cell swelling, induced by cooling. These volume-dependent permeabilities are blocked at 1 degrees C and revealed by rewarming.

Animals↗
PubMed1977

[Regulation of isolated rat hepatocyte volume in hypoosmotic media].

Isolated hepatocytes behave like osmometers immediately after an incubation in hypo-osmotic media. During long-term incubation periods they recover their normal volume either in the absence or in the presence of ouabain. The volume regulation is parlty due to a decrease in intracellular potassium and amino acid contents.

Amino Acids↗