Effect of the lipophilic o-naphthoquinone CG 10-248 on rat liver mitochondria structure and function

CG 10-248 (3,4-dihydro-2,2 dimethyl-9-chloro-2H-naphtho[1,2b]pyran-5,6-dione), a beta-lapachone analogue, modified the ultrastructure of rat liver mitochondria in vitro, in the absence of added oxidizable substrates. The condensed mitochondrial state was replaced by the orthodox or swollen state to a significant degree. The number of modified mitochondria depended on incubation time and quinone concentration, in the 25-100 microM range. Under the same experimental conditions, mitochondrial respiration was uncoupled as indicated by the increase in the rate of succinate oxidation by controlled mitochondria in metabolic state "4" (not in state "3"), and by the activation of latent F0F1-ATP synthase. Taking into account structural similarities, the results reported here may be valid for other o-naphthoquinones, such as beta-lapachone.

Effect of dyskinetoplastic agents on ultrastructure and oxidative phosphorylation in Crithidia fasciculata

Ethidium bromide (EB) is an intercalating agent which binds specifically to the kinetoplast (mitochondrial) DNA (kDNA) of trypanosomatids. Accordingly, EB inhibits DNA replication, thus inducing dyskinetoplasty. Since in eukariotic organisms mitochondrial DNA encodes the genetic information for cytochromes b, aa3 and F0F1 ATPase, it seemed of interest to establish whether a similar effect occurs in Crithidia fasciculata, a trypanosomatid used for assay of potential trypanocidal drugs. Culturing of C. fasciculata in the presence of EB inhibited growth and induced dyskinetoplasty, as confirmed by electron microscopy. The kinetoplast of EB-cultured crithidia lost its characteristic arc shape, it was misplaced in the cell cytoplasm its matrix structure and membrane differentiation were specifically modified. Dyskinetoplasty decreased crithidia respiration and oxidative phosphorylation, as indicated by the lower ATP level, ATP/ADP ratio and adenylate energy charge. The interference of EB with kinetoplastic constituents synthesis was confirmed by the lack of action of EB on crithidia in the stationary phase of growth, that ruled out direct inhibition of oxidative phosphorylation enzymes. The lipophilic o-naphthoquinone beta-lapachone produced structural alterations in kinetoplast membranes, that correlated with inhibition of oxidative phosphorylation. These latter effects involved free radicals since they were prevented by free radical scavengers.

Atrial natriuretic factor in two kidney - two clip renovascular hypertension in the rat

Hig levels of circulating atrial natriuretic factor (ANF) have been reported in several physiopathologic conditions like hypertension, heart and renal failure, pregnancy and high sodium intake. Nevertheless, neither relationships with water-sodium space regulation nor the role of an ANF vascular relaxant effect have been yet defined. The aim of present experiments was to characterize the contribution of circulating ANF and its vascular relaxing effects in the two kidney-two clip (2K2C) experimental model of renovascular hypertension. Complementary, plasma metabolites nitrite/nitrate of nitric oxide (NO) was examined because of mediation for both (NO an ANF) through cGMP. The results showed (two-four weeks after surgery): indirect sistolic blood pressure (mmHg), 186 + 4 in HT and 122 + 1 in SH (p<0.001); a significant increase of plasma ANF (fmol/ml) in HT (n = 7, 1221 + 253) vs. SH (n = 9, 476 + 82; p < 0.02). Nitrate/nitrite plasma concentrations (mumol/l) were mpt different between SH and. The relaxant effect of ANF (10(-9), 10(-8) and 10(-7) M) on phenylephrine (3,5 x 10(-6) M) contracted rings from HT rats was smaller than SH rats (10(-8) M, p < 0.05). Contractions to phorbol 12, 13-dibutyrate (seven weeks after surgery) were significantly higher in rings from HT rats (p < 0.001). We conclude: 1) in addition to decreased granularity in atrial myocardiocytes, high circulating values of ANF here described suggest an increased turnover of the peptide in 2K2C hypertensive rats; 2) lower significant vascular relaxant effects in HT rats would indicate down regulation of ANF receptors in this model; the latter would derive from high plasma ANF concentration and, tentatively, because of greater activity of protein kinase C in the vascular wall; 39 similar values of plasma nitrite/nitrate in SH and HT rats would indicate a comparable NO circulating availability in both groups.