COMPARATIVE TOXICOLOGICAL STUDIES OF BUTYL NITRITES IN MICE

DAVID PHILIP MCFADDEN, Purdue University

Abstract

Butyl nitrites are presently widely abused to alter consciousness, stimulate dancing and intensify sexual experiences. Little research has been performed in order to determine the possible hazards of butyl nitrite abuse. This thesis is presented in an attempt to fill this void. Techniques for purity analysis using GLC, synthesis and storage precautions for butyl nitrites have been presented. Due to the instability of butyl nitrites, the potential for human exposure to butyl nitrite decomposition products exists. Butyl nitrite intraperitoneal and per os median lethal dose (LD50) values were determined. Animals died several days after administration of sec-butyl nitrite (sBN) and tert-butyl nitrite (tBN) by the intraperitoneal route and after administration of all of the butyl nitrites by the per os route. Gross post-mortem examination suggests that liver damage may account for the delayed lethality. LD50 studies using butyl alcohols demonstrated hepatotoxicity similar in appearance and rate of development to butyl nitrites. This suggests that butyl alcohols, produced from butyl nitrite metabolism, may play a role in the damage to the liver. The following results suggest that methemoglobin (metHb) formation is the major toxicity during or immediately after an acute butyl nitrite exposure: (1) The order of potency is nBN > iBN > sBN > tBN using butyl nitrite median lethal concentrations (LC50) at one hour, in vivo metHb forming capabilities, and in vitro metHb forming capabilities. (2) Methylene blue pretreatment (50 mg/kg, intraperitoneal, 15 minutes) not only decreased the levels of metHb formed in animals exposed to butyl nitrites, but also antagonized butyl nitrite-induced lethality. (3) Toxic levels of metHb were observed for each of the butyl nitrites when mice were exposed to lethal concentrations of butyl nitrites. The following results indicate that metHb is not the sole toxicity during or immediately after an acute tBN exposure: (1) Methylene blue pretreatment antagonized isobutyl nitrite (iBN), n-butyl nitrite (nBN) and sBN toxicity more than tBN toxicity. (2) MetHb levels in animals exposed to lethal concentrations of tBN are significantly less than metHb levels in animals exposed to lethal concentrations of the remaining butyl nitrites. The more potent butyl nitrites appear to have greater stability in aqueous medium and more rapid decomposition in fresh whole mouse blood in vitro. This suggests that the parent compound may be capable of oxidizing hemoglobin (Hb) and that the broad range of butyl nitrite potency is due to the Hb reactivity. Subchronic butyl nitrite exposure was demonstrated to cause an increase in spleen and lung weight. The increased spleen weight may be due to an extra load of erythrocyte destruction. The increased lung weight was shown not to be simply due to edema. Plasma isocitrate dehydrogenase levels suggest subchronic butyl nitrite exposure does not cause liver damage in mice. However, liver microsomal glucose-6-phosphatase levels were significantly decreased by subchronic iBN exposure. This suggests liver damage. Liver microsomal cytochrome P-450 levels were significantly decreased by subchronic nBN exposure. This is probably due to the nitrite ion since sodium nitrite has been previously shown to decrease cytochrome P-450 levels. A preliminary study of subchronic iBN exposure on metHb levels indicates that the metHb reductive systems show signs of fading. Pretreatments (intraperitoneal, 15 minutes) with ascorbic acid, methylene blue, sodium selenite and toluidine blue were shown to antagonize per os iBN lethality. Post-treatment (intravenous, immediately) with ascorbic acid demonstrated some protection against per os iBN lethality. Methylene blue, toluidine blue and sodium selenite (intravenous) and 100 percent oxygen post-treatments revealed little or no protection against per os iBN lethality.

Degree

Ph.D.

Subject Area

Pharmacology

COinS