Hormonal control of carbohydrate and lipid metabolism and drug induced alterations

Some approaches to the pharmacology of multisubstrate enzyme systems

Analytical and exploratory in vitro, in situ and in vivo, physio-pharmacotoxicology, from enzymology to population epidemiology, now embraces those approaches that correlate complex dynamic multisubstrate kinetics through conventional and more recent non-invasive quantitative methodologies. Basically, substrates may be classed as pertaining to fundamental energy turnovers (first-order cellular metabolic pathways or networks) and to iso- vs allosteric modulator systems (second-order metabolic control network). Pairs of substrates and cofactors set-up the third-order multienzyme-receptor patterns, which in intact, native in vivo structures establish and maintain the compartmentalized, dynamically superimposed overall coordination of local redox and phosphate potentials. Perturbations of the various levels of the metabolic hierarchy induced by drugs, as well their relaxations, can be readily submitted to non-invasive kinetic analysis. Both indirect and direct titrations of substrate levels, their modelling and statistical ad hoc evaluations of their interrelations can lead to the identification of the multiple sites involved in drug effects as structured at the different orders/levels of concomitant functional variations. Fractal geometries contribute towards defining the space- and time-related events.

[Influence of thyroid state on noise-induced cochlea damage (author's transl)]

Guinea pigs were exposed to pure tone noise (2.7 kHz, 130 dB, 1 h) and cochlear microphonic potentials were measured after 5 days. It is possible, to modify the resulting damage by experimentally altering the rate of metabolism by regulating the function of the thyroid gland. (table: see text) A hypofunction of the thyroid gland during sound exposure lessens, an over-function aggravates the damage. This effect possibly results from the influence on the metabolism exerted by the adenylic system. This conclusion leads to new viewpoints concerning prophylaxis, therapy and metaphylaxis in cases of noise deafness.

Non-specific inhibition of membrane-ATPase by amiloride: a comparative in vivo and in vitro study with ouabain

The submaxillary duct epithelium, which actively transports Na+ (rabbit) and, in addition, K+ and H+/HCO-/3 (rat), was used as a model epithelium to compare the effects of ouabain and amiloride on transport parameters. 1. Ouabain was only effective from the interstitial side, amiloride, however, only from the luminal side. Amiloride induced effects on transport of the ions were seen within less than 1 s, ouabain effects, however, only after minutes. 2. Ouabain inhibited in a parallel fashion the Na+ transport potential and the Na+-K+-ATPase activity. It had no effect on the Mg2+-ATPase and the HCO-/3-ATPase. 3. Amiloride also inhibited the Na+ transport potential and the Na+-K+-ATPase; however, the Na+ transport potential was significantly more sensitive to amiloride than the Na+-K+-ATPase. 4. Amiloride inhibited in a similar fashion the Na+-K+-ATPase, the Mg2+-ATPase and the HCO-/3-ATPase, but did not influence active HCO-/3 secretion. 5. It is concluded that the amiloride induced effects on the membrane ATPases are non-specific.

The potentiation of rat uterine inhibitory responses to noradrenaline by theophylline and nitroglycerine

1. Dose response curves for noradrenaline were determined before, during and after pretreatment with a variety of agents. The inhibitory response to noradrenaline on the isolated rat uterus was measured according to its ability to inhibit an acetylcholine induced contraction.2. Theophylline, an agent that inhibits phosphodiesterase and increases cyclic AMP levels in the rat, potentiated the response to noradrenaline.3. Pretreatment with cocaine had no significant effect on the potentiation of the noradrenaline response by theophylline.4. Theophylline potentiated the inhibitory response to nitroglycerine.5. Pretreatment with nitroglycerine also potentiated the inhibitory response to noradrenaline.6. Theophylline appears to produce a potentiation of the inhibitory effect of noradrenaline on the rat uterus by means of a non-specific mechanism.