Does stress influence ampicillin concentration in serum and tissues?

Exercise produces changes of drug levels in plasma and increases the concentration of free fatty acids (FFAs), which may interfere with drug-protein binding. FFAs seem to play an antagonistic role to drugs since they have a strong binding capacity to serum albumin. The aim of this study was to evaluate the influence of the consecutive exercise-induced stress in ampicillin levels. Two groups of Wistar rats were used. Group A consisted of six subgroups that were subjected to cold swimming (4 degrees C) for 5, 10, 15, 20,25, 30 days respectively. Group B was the control group. The animals were injected im. with ampicillin (1 g/Kg/8h in 5 doses). Results showed that exercise enhanced stress parameters (FFAs, adrenal weight, Ht%) and led to an ampicillin increase in all experimental groups comparatively to controls.

[In vivo regulation by calcium of the thyroidal iodine metabolism and its modulation by sodium, in the rat (author's transl)]. / Régulation in vivo par le calcium du métabolisme thyroïdien de l'iode et sa modulation par le sodium, chez le rat.

In vivo experiments, in the rat, using diets deficient in calcium, or sodium or both ions, proved these cations to regulate the thyroidal iodine metabolism. Calcium enhanced iodine entry into the thyroid and the intrathyroidal iodine and T4 pools. T4 level in serum was also increased by calcium. Sodium enhanced iodine entry and secretion. The two cations have local regulatory functions on the thyroid gland and do not affect TSH levels in serum and the hypophysis. The effects of calcium and sodium are interdependent, sodium deficiency suppressed the effects of calcium and the effects of sodium were significantly limited by calcium deficiency. Results from chromatography of the thyroid extracts and data from the literature are compatible with the hypothesis of calcium enhancing iodine entry and accumulation into the thyroid gland mainly through an effect on exocytosis of thyroglobulin, the was this ion enhances exocytosis of protein in stimulus-secretion coupling. An addition to this theory is pur forward in order to reconcile with it the whole set of experimental data obtained with the two cations, in vivo and in vitro, on thyroidal iodine metabolism.

[The stimulation by calcium of the thyroidal iodine metabolism fits into the scheme of "stimulus-secretion coupling" (author's transl)]. / La stimulation par le calcium du métabolisme thyroïdien de l'iode est compatible avec le schéma du "stimulus secretion coupling".

In vivo, in the rat, in nutritional experiments, calcium accelerated iodine entry into the thyroid and augmented the concentration of iodine in the gland (1). These data are compatible with the hypothesis of Ca2+ acting on the thyroid as in "stimulus-secretion coupling" where the cation promotes extrusion of the contents of exocytotic granules (2). The whole set of experimental data from the in vivo work (1, 3) fit into the view that Ca2+ might increase the velocity of iodine entry into and the concentration of iodine in the thyroid by promoting exo cytosis of non iodinated thyroglobulin; and so do data from in vitro experiments in the literature, provided the statement: "Ca2+ is required for the in vitro TSH stimulation of 131I transfer from the intrathyroidal iodide pool into thyroglobulin" (5) is inverted into: "Ca2+ is required for the TSH stimulation of the transfer of Tg into the sites of its iodination"; these are located in the lumen of the follicle (4). The transfer of Tg (= exocytosis) was shown to be limiting factor to the acceleration of iodine binding by TSH, in vivo (6).

[In vivo regulation by calcium of thyroid metabolism of iodine in rats]. / Régulation, in vivo, par le calcium, du métabolisme thyroïdien de l'iode, chez le rat.

In vivo experiments using a calcium deficient or a normal diet, proved that calcium enhance iodine entry and concentration into the thyroid gland of the rat and the intra-thyroidal T4 pool, T4 level in serum was also increased. Peripheral metabolism of T4, serum TSH levels and pituitary TSH contents were unaffected. Calcium has a local regulatory function on the thyroid gland.