No abstract

The kidney's responsiveness to male sexual hormones has been often neglected. Renal secretion of organic anions is higher in male than in female individuals; as a consequence, most of the xenobiotics that are excreted from the organism through this pathway are eliminated more rapidly by males than by female animals. To gain further insight into this issue, we studied in vitro and in vivo characteristics of the transport of p-aminohippurate (PAH), a suitable marker for this system, in male and female rats, under different hormonal conditions. Kinetics of PAH showed a shorter elimination half-time in male than in female rats (t(1/2el): male = 16.2 +/- 2.1 min, female = 25.7 +/- 4.5 min, P < 0.05). Castration of male rats increased t(1/2el) to a value similar to that of female rats (t(1/2el): orchiectomized rat = 28.1 +/- 7.1 min). Testosterone treatment of female rats increased the elimination rate to a value similar to that of male rats. In vitro PAH uptake by renal cortical slices from intact male rats was higher than that by slices from orchiectomized rats. Kinetic analyses of PAH uptake suggest that the difference was caused by a lower number of transporting molecules in orchiectomized than in intact animals, whereas the transporting capacity for each carrier was similar in male and in orchiectomized rats. Our results suggest that testosterone increases the number of functional carriers for PAH in the kidney.

Arthrospira maxima (Spirulina) is considered a nutraceutical or functional food because it provides health benefits and it is used as nephroprotector because it contains nucleophilic compounds as phycobiliproteins and phycocyanin that prevent oxidative stress and cellular damage process. Also, it is known that inorganic mercury is bioaccumulated and exerted kidney toxicity. Despite the nephroprotective effect of Spirulina and its components, there is not enough information about the effect of them on renal function as well as the apoptosis process inhibition. This work aimed to investigate whether phycobiliproteins and phycocyanin of Spirulina can improve HgCl 2 -related glomerular and tubular renal dysfunction as well as the Bax, Bcl 2 , and effectors caspases alterations. Male mice were administrated with Spirulina, phycobiliproteins or phycocyanin 30 min before 5 mg/Kg HgCl 2 administration. The nutraceuticals were administrated for the next 5 days. Then, the mice were euthanized. The renal function, caspases 3 and 9 activities, as well as Bax and Bcl 2 expression were evaluated. Spirulina and its components prevent HgCl 2 -related apoptosis induction and glomerular dysfunction. We concluded that phycobiliproteins and phycocyanin of Spirulina reduce glomerular damage but not the tubular dysfunction in a mercury-related acute kidney injury.

To characterize Ca(2+) transport in newborn rat cortical collecting duct (CCD) cells, we used nifedipine, which in adult rat distal tubules inhibits the intracellular Ca(2+) concentration ([Ca(2+)](i)) increase in response to hormonal activation. We found that the dihydropyridine (DHP) nifedipine (20 microM) produced an increase in [Ca(2+)](i) from 87.6 +/- 3.3 nM to 389.9 +/- 29.0 nM in 65% of the cells. Similar effects of other DHP (BAY K 8644, isradipine) were also observed. Conversely, DHPs did not induce any increase in [Ca(2+)](i) in cells obtained from proximal convoluted tubule. In CCD cells, neither verapamil nor diltiazem induced any rise in [Ca(2+)](i). Experiments in the presence of EGTA showed that external Ca(2+) was required for the nifedipine effect, while lanthanum (20 microM), gadolinium (100 microM), and diltiazem (20 microM) inhibited the effect. Experiments done in the presence of valinomycin resulted in the same nifedipine effect, showing that K(+) channels were not involved in the nifedipine-induced [Ca(2+)](i) rise. H(2)O(2) also triggered [Ca(2+)](i) rise. However, nifedipine-induced [Ca(2+)](i) increase was not affected by protamine. In conclusion, the present results indicate that 1) primary cultures of cells from terminal nephron of newborn rats are a useful tool for investigating Ca(2+) transport mechanisms during growth, and 2) newborn rat CCD cells in primary culture exhibit a new apical nifedipine-activated Ca(2+) channel of capacitive type (either transient receptor potential or leak channel).