P. Kourounakis

Liver ultrastructure during acute stress.

An ultrastructural, morphologic and histochemical study was made on the livers of rats exposed to eight different acute stressors: fasting, cortisol injecions, reserpine injections, restraint, spinal cord transection, immersion in hot water, exposure to cold and forced muscular exercise in a revolving drum. After 48 hours of exposure to stress, electron microscopy of the liver revealed rough endoplasmic reticulum fragmentation and dilatation, glycogen depletion, and mitochondrial enlargment. The most striking change, however, was an increase in the number and size of autophagic vacuoles which were limited by single or multiple membranes. A cytochemical study revealed that in the former case, the vacuolar membranes did not show a glucose-6-phosphatase positive reaction, whereas they did in the latter case. The vacuoles contained acid phosphatase positive material as well as organelles in various stages of degradation. Following exposure to most of the stressors, a marked increase of plasma corticosterone was noted, with a lowered rectal temperature and the appearance of the typical stress triad (adrenal hypertrophy, thymicolymphatic involution and gastrointestinal ulcers). The severity of the morphologic changes appeared to parallel the degree of hypothermia caused by the stressor. The results suggest that autophagy in the liver may be an adaptive response to stressors at the subcellular level.

Effect of phenobarbital or pregnenolone-16α-carbonitrile (PCN) pretreatment on acute carbon tetrachloride hepatotoxicity in rats

Abstract In rats, CCl4 hepatotoxicity (reflected by augmented serum glutamic-pyruvic transaminase activity and hepatic triglyceride content) was diminished by pregnenolone-16α-carbonitrile (PCN) and markedly increased by phenobarbital. PCN, like penobarbital, caused smooth-surfaced endoplasmic reticulum proliferation in hepatocytes and enhanced hexobarbital oxidation, ethylmorphine N-demethylation, cytochrome P-450 and NADPH-cytochrome c reductase activity. Contrary to earlier views, it is concluded that the increase in these parameters is not a prerequisite for augmented CCl4 toxicity. Perhaps the cytochrome P-450 induced by the steroid and barbiturate has different catalytic properties, which are responsible for variations in the response to CCl4.

Fine Structural Changes in the Liver of Young and Old Rats as Influenced by Microsomal Enzyme Inducers

When given orally to young and old rats, pregnenolone-16 alpha-carbonitrile, spironolactone, or phenobarbital, known microsomal enzyme inducers, caused an increase in smooth endoplasmic reticulum. Dexamethasone, while a potent microsomal enzyme inducer, did not cause smooth endoplasmic reticulum increase. In both untreated and treated old rats, there was dilatation and vesiculation of rough endoplasmic reticulum with occasional granular material present in vesicles. Cytoplasmic lipid droplets of various sizes were frequent. Some mitochondria exhibited polymorphism and a variation in matrical density. Lysosomes and autophagic vacuoles as well as lipid droplets of various sizes were frequent in all groups. These results show that microsomal enzyme inducers influence the subcellular structure of hepatocytes in old rats.

Prevention of organomercurial intoxication by thyroid deficiency in the rat

Abstract In the rat, thyroparathyroidectomy or antithyroid drugs such as propylthiouracil and methimazole protect against acute poisoning with diphenyl or dimethyl (DMM) mercury. Though histologically thyroparathyroidectomy only slightly diminishes the early liver changes induced by DMM, it accelerates hepatic restoration processes. Serum glutamic-pyruvic transaminase activity and hexobarbital sleeping time, which are enhanced by DMM, are significantly decreased in thyroparathyroidectomized rats 48 hr after DMM administration. Kidney lesions are prevented by thyroid deficiency.

Comparative studies on the effect of adrenocorticotrophic hormone (ACTH) and pregnenolone-16α-carbonitrile (PCN) upon drug response and distribution in rats

Abstract The effects of pretreatment with pregnenolone-16α-carbonitrile (PCN) or crystalline adrenocorticotrophic hormone (ACTH) and depot ACTH were investigated in female rats given picrotoxin, nikethamide, succinylcholine, strychnine, ethylmorphine, dioxathion, acetanilide, aniline, N -methylaniline, pancuronium, allopurinol, methyprylon, barbital, cyclobarbital, hexobarbital, phenobarbital, zoxazolamine, mephenesin, carisoprodol, sodium aurothiomalate or N -carbamoylarsanilic acid. Both ACTH and PCN offered significant protection against most of the drugs, but nikethamide and dioxathion toxicity was diminished solely by PCN, whereas that of aniline, N -methylaniline, barbital and phenobarbital was decreased by ACTH alone. Time-sequence studies revealed that a single injection of depot ACTH, or PCN gavage, 24 hr prior to zoxazolamine, significantly shortened paralysis. However, a few days of pretreatment with PCN were needed for maximal protection. ACTH, unlike the steroid, reduced zoxazolamine paralysis even in the presence of diethylaminoethyl-2,2-diphenylvalerate (SKF 525-A), a microsomal enzyme inhibitor. Protection by ACTH was not associated with decreased concentrations of zoxazolamine in blood, brain and muscle (syntoxic action). In contrast, PCN lowered the drug level, probably through increased biotransformation and/or excretion (catatoxic action). These findings furnish additional support to the view that catatoxic steroids mostly operate via the induction of drug-metabolizing enzymes in hepatic microsomes, while syntoxic agents augment resistance, probably through altered drug distribution, interactions at receptor sites or decreased receptor sensitivity.

Effect of Pregnenolone-16α-Carbonitrile on Bilirubin- and Sulfobromophthalein-Binding to Hepatic Y and Z Proteins in the Rat

Pregnenolone-16 alpha-carbonitrile (PCN), administered twice daily p.o. for 3 days at a dose level of 20 mumol/100 g body weight, significantly enhances in vivo binding of 14C-bilirubin and sulfobromophthalein (BSP) to hepatic Y and Z proteins in female Charles River CD rats. 14C-bilirubin-binding to Y protein showed a 61% increase, while binding of the same moiety to the Z protein fraction was augmented by 59%. BSP-binding in vivo demonstrated rises of 114 and 71% in relation to Y and Z proteins, respectively. These data correlate well with previous investigations in which PCN was found to have a beneficial influence on experimentally induced hyperbilirubinemias and, furthermore, there is an indication that phenobarbital, another potent microsomal enzyme inducer, acts via a similar mechanism.

Effect of Pharmacologic Conditioning on Sulfadiazine Toxicity and Concentrations in Plasma

In female rats, pretreatment with pregnenolone-16α-carbonitrile (PCN), spironolactone or CS-11 reduced the toxicity of sulfadiazine; the first two steroids also decreased its concentrations

Effect of Various Steroids and Nonsteroidal Microsomal Enzyme Inducers upon Propoxyphene Intoxication

In rats, severe propoxyphene intoxication can be diminished more effectively by some catatoxic steroids than by known nonhormonal hepatic microsomal drug-metabolizing enzyme inducers, such as phenobar

Protection against phenylisothiocyanate by various steroids, phenobarbitone and diphenylhydantoin

and the supernatant also assayed for pepsin. Portions of homogenate and of supernatant were also assayed for nitrogen (Kjeldhal). Further groups of rats were similarly treated and the number of animals with gastric lesions and the severity of these graded by an arbitrary scale from 0 to 4+ was recorded. The pepsin activity of stomach tissue is always lower in the ulcerated animals (Table 1). Oxyphencyclimine and, to a lesser extent, atropine reduced the ulceration index and simultaneously increased the stomach tissue pepsin activity of the animals with reserpineand phenylbutazone-induced ulcers. In these groups there was a good relation between the enzyme activity and the severity of gastric lesions although the two parameters were not always proportionally related.

Protection against the neurolathyrism produced by arsanilic acid in the rat

Abstract In the rat, intoxication with arsanilic acid manifests itself in the form of nervous disturbances clinically indistinguishable from neurolathyrism. This intoxication is aggravated by two potent catatoxic steroids (agents which increase the destruction of toxic substances), pregnenolone-16α-carbonitrile or “PCN” and ethylestrenol. On the other hand, triamcinolone, desoxycorticosterone and thyroxine offer considerable protection against this arsenical, although they are devoid of catatoxic potency against other substrates. These pronounced effects of hormones upon arsanilic acid intoxication are especially noteworthy in view of the fact that, according to current views, arsanilic acid is not subject to biotransformation, being excreted unchanged at least under ordinary conditions, that is, in the absence of pretreatment.