PLASMA 8-ENDORPHIN-LIKE IMMUNOREACTIVITY AND ITS qARIATZONS IN BABOONS E. V. Golanov, A. A. Fufacheva, and S. B~ Parin UDC 612.129:[547.95:547.943]~06-019 KEY WORDS: endorphin-like immunoreactivity, blood plasma, baboons. Endogenous opioid peptides are implicated in many physiological processes, including formation of the response of the organism to stress [i]. One of the most important components of the system of endogenous opioid peptides in 8-endorphin. An important physiological role has been ascribed to 8-endrophin circulating in the blood stream [4]. Formed as a result of hydrolysis of 8-1ipotropin, it enters the blood stream from the anterior and intermediate lobes of the pituitary [6]. The plasma 8-endorphin concentration in animals of different spe- cies varies within considerable limits. In cats, for instance, it is measured in hundreds of picograms per milliliter [2], in rats in tens of nanograms per milliliter, and in man from units to tens of picograms per milliliter [5, 9]. The aim of this investigation was to determine the level of B-endorphin-like immunore- activity (B-ELIR) in the blood plasma of baboons and to study its changes in certain situa- tions. EXPERIMENTAL METHOD Exveriments were carried out on six baboons (Papio ~madryas) weighing 5.5-8~ kg. Be- tween5 and 7 days before the beginning of the experiments electrodes were implanted into var- ious brain structures of the baboons under pentobarbital anesthesia (40 mg/kg~ in~ravenously)~ Stainless steel electrodes 0.8 mm in diameter were insulated over their whole length except the tip (0.5 mm). Immediately after the operation the animals were placed in primatologic chairs, in which they remained throughout the experiment (3-4 weeks). Blood (3-4 ml) was taken from the cubital vein of the animals by means of a polyethylene syringe and quickly trans- ferred into a polyethylene test tube (after preliminary addition or EDTA), kept on ice. After centrifugation the blood plasma was frozen and stored at -20~ until required for analysis. Blood was taken between noon and 4 p.m. For radioimmunoassayof B- ELIKiint the blood plasma, a standard kit from INC (USA) and the appropriate technique were used. In some cases radio- immunoassay of total 8-ELIR/B-lipotropin-like immunoreactivity (B-LLIR) also was carried out with the aid of a standard kit from "Seragen" (USA). In this case, by substracting the 8-ELIR from the total B-ELIR + 8-LLIR, the level of 8-LLIR could be determined. Electrical stimula- tion (ES) of the brain structures was carried out by monopolar square pulses with a duration of i0 msec, frequently 50 Hz, and current strength 4-5 ~A. The animals were killed by injection of large doses of pentobarbital. Hemorrhagic shock was produced by bleeding from the brachial vein of anesthetized animals (chloralose, 80 mg/kg, intravenously). The position of the elec- trodes was verified histologically in serial brain sections fixed beforehand in formalin so- lution, and cut on a freezing microtome. The sections were photographed without preliminary staining. EXPERIMENTAL RESULTS The background plasma 8-ELIR level of the baboons, in a state of quiet wakefulness, was 8.0 = 1.0 fmoles/ml,~ and the minimal and maximal values were 5 and ii fmoles/ml respectively (28.0 • 5.0 pg/ml, n= i0). The total level of B-ELIR and ~-LLIR was 134 • 24 pg/ml (minimum 84 pg/ml, maximum 162 pg/ml, n = ii). By subtraction, the 8-LLIR level was 90 • I0 fmoles/m! (from 5 to ii fmoles/ml, 104.0 • 19.0 pg/ml, n = 7). The ratio of the molar concentration of B-ELIR to that of B-LLIR averaged 0.9 • 0.i (0.8-1.2) o A. L. Myasnikovlnstituteof Clinical Cardiology, Ail-Union CardiologicScientificCenter, Academy of Medical Sciencesof the USSR; Moscow. Institute of Experimental Pathology andTher- apy, Academy of Medical Sciences of the USSR; Sukhum i. Translated fromByulleten' ~ksperiL mental'no• Biologii~i Meditsiny, Vol; ZOO, No, 12~ pp. 677-679, December, 1985. Original ar- ticle submitted February 18, 1984. 0007-4888/85/0012-1653509.50 9 1986 Plenum Publishing Corporation 1653