Influence of lindane on the fluidity of the rat ventral prostate membranes

A novel aspect of lindane testicular toxicity: in vitro effects on peritubular myoid cells

The in vitro effects of the insecticide lindane have been investigated in rat testis peritubular myoid cells (PMCs). Upon PMC exposure to lindane, polarity increase and decrease of dipole dynamics were seen at the membrane level (EC50 20 microM), leading to a partial dissipation of the membrane intrinsic dipole potential. The initial membrane depolarization was increased by Cl- efflux and limited by Ca(2+)-activated repolarizing currents. Concomitantly, lindane produced an increase in [Ca2+]i (EC50 125 microM) resulting from both Ca2+ release from an inositol 1,4,5-trisphosphate-sensitive intracellular store and a voltage-dependent Ca2+ influx from the extracellular medium. Of particular interest from a toxicologic point of view, insecticide concentrations well below those effective in altering ion homeostasis potently inhibited both [Ca2+]i increase and contraction induced by the natural agonists vasopressin and endothelin-1 (IC50s < 10 microM). These data demonstrate that PMCs are highly susceptible to lindane and suggest that the insecticide may exert testicular toxicity by interfering with hormone-regulated PMC function.

Hexachlorocyclohexanes affect the arachidonic acid release from phosphatidylinositol but not from other phospholipid classes in tubular cell cultures

Gamma- and delta-isomers of hexachlorocyclohexane caused marked decreases in the levels of radioactive phospholipids, and increases in the levels of [3H]arachidonate incorporated into free fatty acids in rat renal tubular cells. The increased radioactivity of free fatty acids arises from the decrease of [3H]arachidonate incorporated into phosphatidylinositol, but not into phosphatidylcholine, phosphatidylserine or phosphatidylethanolamine. This fact suggests that phosphatidylinositol can be broken down to the fatty acid from the sn-2 position and lysophospholipid by a phospholipase activity increased by hexachlorocyclohexanes. The observed specific toxicant action could be achieved in two ways: (a) operating upon a specific phospholipase A2 that acts on phosphatidylinositol, but not on other phospholipids as substrates and/or (b) involving substrate-phospholipase A2 interactions. Interestingly, the observed effect of the delta-isomer was more pronounced than that of the gamma-one.

Role of lindane in membranes. Effects on membrane fluidity and activity of membrane-bound proteins

The influence of lindane (gamma-hexachlorocyclohexane) on fluidity of plasma membranes from rat renal cortical tubules has been investigated. Preincubation with lindane increased membrane fluidity. This effect was accompanied by (i) a decrease in the transport of glucose with regard to the controls and (ii) an inhibition of the beta-adrenergic stimulatory activity upon cyclic AMP accumulation. However, a significant decrease of the membrane fluidity was found when rats were injected with lindane for 12 days. The injection of lindane exerted the opposite effect on the membrane proteins, the glucose transporter and the beta-adrenergic receptor, enhancing the glucose uptake and increasing the isoproterenol-stimulated cycle AMP accumulation. A possible explanation of the difference could involve a resistance to membrane disordering by lindane through a regulatory mechanism that would balance the activity of many lindane-sensitive proteins in insecticide-injected rats.

Lindane-induced modifications to membrane lipid structure: effect on membrane fluidity after subchronic treatment

Chronic lindane intoxication by injecting subcutaneously the toxicant, resulted in an altered lipid pattern in rat ventral prostate membranes. An increase of membrane fluidity was also observed using a fluorescence polarization technique. When in vitro experiments were carried out with both treated and untreated rats, an interesting lack of parallelism was found, which could indicate the development of a resistance to membrane disordering by lindane. The observed changes in cholesterol and phospholipid composition are also consistent with the hypothesis that lindane perturbs the lipid matrix of membranes, possibly inducing complex compensatory changes in the membrane lipid composition.

The effects of different hexachlorocyclohexanes and cyclodienes on glucose uptake and inositol phospholipid synthesis in rat brain cortex

The inositol lipids from rat brain miniprisms were deacylated and separated by anion-exchange chromatography in order to determine whether or not gamma-hexachlorocyclohexane (gamma-HCH, lindane) and related compounds affect the different phosphatidylinositols. The incorporation of myo-[2-3H]inositol into phosphatidylinositol, phosphatidylinositol monophosphate and phosphatidylinositol bisphosphate were inhibited by lindane and its delta-HCH isomer. The inhibitory effects on phosphatidylinositol synthesis are not prominent in alpha-HCH and they are not significant with the beta-HCH and cyclodienes. The results presented here indicate that the inhibitory effect of lindane and delta-HCH on the phosphatidylinositol metabolism was no exclusively due to an interference with glucose transport. Lindane-treated miniprisms showed decreased myo-[2-3H]inositol uptake and, proportionately, an even greater inhibition of inositol phospholipid synthesis. Cellular uptake can, therefore, not account for all of the lindane inhibition.