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Rat lymphocytes incubated under hypoxic conditions in vitro show a time-dependent release of intracellular enzymes. As reported previously, enzyme release (lactate dehydrogenase) is decreased by metabolite, notably ATP and glucose, that contribute towards lymphocyte energy metabolism. The action of purine nucleosides in relation to enzyme release was investigated. Inosine was shown to decrease significantly lactate dehydrogenase release, whereas adenosine exerted a supportive action only at concentrations less than 0.5 mmol/l. Inosine decreased enzyme efflux maximally at concentrations of at least 2--3 mmol/l. The mechanism of inosine action was deduced to be primarily ribose 5-phosphate formation and its subsequent metabolism by energy-yielding pathways. Inosine was presumed also to enter the purine 'salvage pathway' and thereby maintain intracellular adenine nucleotide pools.

The alterations in the immune system caused by ethanol appear to be a complex combination of direct and indirect effects. The role of ethanol as an osmolyte has previously been studied in this laboratory with rat splenocytes. In the present study the osmotic effects of ethanol were investigated in lymphocytes from human normal subjects and alcohol abusers. Mitogen-stimulated lymphocytes were cultured in vitro with ethanol in hyperosmotic isotonic or iso-osmotic hypotonic conditions. The former conditions mimic the physiological situation where ethanol increases osmolality in an electrolyte-balanced environment. Under these conditions, lymphocyte proliferation was unaffected. Ethanol addition in iso-osmotic hypotonic conditions, where there is electrolyte imbalance, was associated with inhibition of T-lymphocyte proliferation. Hyperosmotic hypertonic solutions in the absence of ethanol also resulted in inhibition of T-lymphocyte proliferation. Electron microscopy and measurement of cell viability and metabolic activity (lactate and ATP levels) indicated that the decreased proliferation associated with NaCl-induced hyperosmotic hypertonic conditions was at least partially attributable to cell death together with, and possibly caused by, detrimental effects on mitochondria. Conversely, decreased T-lymphocyte proliferation in iso-osmotic hypotonic high ethanol solutions, appeared not to be due to changes in cell viability, nor alterations to energy metabolism. It is proposed that ion fluxes involved in the maintenance of cell volume, in particular K[sup +] movement, may be important in facilitating normal lymphocyte proliferation in the presence of ethanol in pathological conditions associated with electrolyte imbalance. [ABSTRACT FROM AUTHOR]

The amino acid L-glutamine is essential for the function of both resting and stimulated lymphocytes, and its uptake is significantly increased after stimulation. The effects of ethanol on the immune system appear to be widespread and significant, and its role as an osmolyte has recently been proposed to be important. The in vitro effect of concurrent glutamine deprivation and ethanol exposure in different osmotic conditions was investigated with respect to the proliferative capability of lymphocytes in vitro from both alcohol abusers and non-abusers, and also the kinetics of glutamine transport across peripheral blood lymphocytes (PBL) membranes from nonabusers. In a physiologically normal situation ethanol increases osmolality, and tonicity remains balanced. However, in situations of electrolyte imbalance ethanol addition may result in osmolality remaining near normal levels, but with hypotonicity. It was found that a lack of glutamine and iso-osmotic hypotonic high ethanol concentrations caused a greater inhibition of mitogen-stimulated lymphocyte proliferation than either factor alone. This was true for PBL from both non-abusers and abusers of alcohol.There was no change in membrane permeability and active transport of glutamine into lymphocytes from non-abusers that were stimulated in vitro in various conditions of ethanol, osmolality and tonicity. While lymphocyte proliferation may be inhibited in certain conditions and this is further affected by a lack of glutamine, the capacity for active glutamine transport was maintained, perhaps due to its essential role in lymphocyte metabolism. [ABSTRACT FROM AUTHOR]