RESUMEN

After the application of 2.36 Curies per millimole [2,3-(3)H]gibberellin A(20) (GA(20)) to 21-day-old maize (Zea mays L., hybrid CM7 x CM49) plants, etiolated maize seedlings, or maturing maize cobs, a number of (3)H-metabolites were observed. The principal acidic (pH 3.0), ethyl acetate-soluble metabolite was identified as [(3)H]GA(1) on the basis of co-chromatography with standard [(3)H]GA(1) on SiO(2) partition, high resolution isocratic elution reverse phase C(18) high performance liquid chromatography and gas-liquid chromatography radiocounting. Two other acidic metabolites were identified similarly as [(3)H]GA(8) and C/D ring-rearranged [(3)H]GA(20), although gas-liquid chromatography radiocounting was not performed on these metabolites. Numerous acidic, butanol-soluble (e.g. ethyl acetate-insoluble) metabolites were observed with retention times on C(18) high performance liquid chromatography radiocounting similar to those of authentic glucosyl conjugates of GA(1) and GA(8), or with retention times where conjugates of GA(20) would be expected to elute. Conversion to [(3)H]GA(1) was greatest (23% of methanol extractable radioactivity) in 21-day-old maize plants. In etiolated maize seedlings, the C/D ring-rearranged [(3)H]GA(20)-like metabolite was the major acidic product, while conversion to [(3)H]GA(1) was low.

RESUMEN

Cholesterol biosynthesis from DL-[2-14C]mevalonic acid ([14C]MVA) was demonstrated in ovine ovarian follicles and isolated thecal tissues and granulosal cells incubated in vitro. Thecal tissues more readily synthesized cholesterol than did granulosal cells when incubated separately, but in the intact follicle the newly synthesized cholesterol distributed evenly between the two tissue layers, indicating that the theca could act as a supplementary source of cholesterol for the granulosal cells. Human chorionic gonadotrophin (hCG) added to the incubation medium was found to inhibit cholesterol biosynthesis from [14C]MVA by intact follicles and isolated thecal tissues, but not granulosal cells. This hCG-induced inhibition was evident in whole follicles incubated for 12--48 h, but not at 3--6 h, and was demonstrated in thecal tissues incubated for 3 h. In all cases where inhibition of cholesterol biosynthesis was observed, 14C label accumulated in a product characterized by thin layer and vapour phase chromatography as lanosterol, implying that the hCG block lies between lanosterol and cholesterol. Treatment of follicles with hCG also reduced the amount of 14C label incorporated into the cholesteryl ester fraction. These changes were accompanied by a corresponding reduction in the tissue content of cholesteryl ester, but there were no changes in the specific activities to indicate that newly synthesized cholesteryl ester was used selectively as a substrate for progestin biosynthesis.

Asunto(s)

Colesterol/biosíntesis , Gonadotropina Coriónica/farmacología , Folículo Ovárico/metabolismo , Animales , Colesterol/análogos & derivados , Ésteres del Colesterol/metabolismo , Femenino , Células de la Granulosa/metabolismo , Humanos , Técnicas In Vitro , Lanosterol/metabolismo , Piperidinas/farmacología , Compuestos de Amonio Cuaternario/farmacología , Ovinos , Escualeno/metabolismo , Células Tecales/metabolismo

Asunto(s)

Colesterol/biosíntesis , Gonadotropina Coriónica/farmacología , Ovario/metabolismo , Animales , Femenino , Ovinos

RESUMEN

Three plant-growth retardants 2'-isopropy1-4'-(trimethylammonium chloride)-5-methylphenylpiperidine carboxylate (Amo 1618), beta-chloroethyltrimethylammonium chloride, and tributyl-2, 4-dichlorobenzylphosphonium chloride were tested for their effects on sterol production in, and growth of tobacco (Nicotiana tabacum) seedlings. As the concentration of each retardant increased, there was an increased inhibition of the incorporation of dl-2-(14)C-mevalonic acid into sterol (particularly desmethylsterol) fractions and an increased retardation of stem growth. Growth retardation was observed with both single and repeated retardant treatments, and with Amo 1618, in particular, a close quantitative relationship between inhibition of sterol biosynthesis and stem growth was obtained. Gibberellic acid completely overcame retardant effects and application of sterols also restored normal growth. It is concluded that the concept of causality in the relationship between growth retardation and gibberellin biosynthesis is probably premature, since growth retardants have a more general inhibitory action on isoprenoid biosynthesis in plants.

Asunto(s)

Acetatos/metabolismo , Colesterol/biosíntesis , Reguladores del Crecimiento de las Plantas/farmacología , Acetatos/sangre , Factores de Edad , Animales , Isótopos de Carbono , Colesterol/sangre , Cromatografía de Gases , Glucosa/metabolismo , Inyecciones Intraperitoneales , Hígado/metabolismo , Masculino , Ácido Mevalónico/metabolismo , Reguladores del Crecimiento de las Plantas/toxicidad , Ratas , Estimulación Química

RESUMEN

2-Isopropyl-4-dimethylamino-5-methylphenyl-1-piperidine carboxylate methyl chloride, 90%, applied to rootless tobacco (Nicotiana tabacum cv. Samson) seedlings inhibits the incorporation of (14)C-mevalonate into sterols. Concomitantly, the retardant causes the accumulation of squalene-2,3-epoxide, an intermediate in sterol biosynthesis. The results with tobacco are identical to those produced by the retardant in cell-free rat liver preparations.