Ovarian steroid metabolism and oestrogens in the corpus luteum of the tammar wallaby

Ovaries were obtained from tammar wallabies at various stages of the reproductive cycle to examine the occurrence of oestrogens in corpora lutea, and the synthesis and metabolism of steroids in the corpus luteum and ovarian cortical and interstitial tissues. Corpora lutea contained oestradiol-17 beta and oestrone during embryonic diapause and at all stages of pregnancy studied after blastocyst activation. Aryl sulphatase, 3 beta-hydroxysteroid dehydrogenase and 17 beta-oxidoreductase were shown to be present in luteal and other ovarian tissues by incubation in vitro with labelled substrates. Aromatase was undetectable in corpora lutea or in interstitial tissue, but was present in the ovarian tissues (including follicles) which remained after removal of corpora lutea. The probable source of the oestrogens detected in the corpus luteum is discussed in relation to their role in the inhibition of follicular development during embyronic diapause.

Mammary gland lactose, plasma progesterone and lactogenesis in the marsupial Macropus eugenii

Mammary gland lactose concentrations in pregnant tammar wallabies remained low at 115 +/- 24 (S.E.M.) micrograms/g wet weight of tissue until immediately before parturition, then increased to 1274 +/- 262 micrograms/g after birth. Concentrations in non-pregnant cyclic animals were generally low (143 +/- 36 micrograms/g), but were raised in three animals around the time of oestrus. Removal of the corpus luteum on day 18 of pregnancy or the oestrous cycle caused an increase in lactose concentrations in both lutectomized and sham-operated animals. This occurred despite a significant lowering of peripheral plasma progesterone concentration in only the lutectomized group. Plasma cortisol concentrations were high in some of these animals, but showed no consistent relationships with the raised lactose concentrations. The increased peripartum lactose concentration normally coincides with a sharp fall in peripheral plasma progesterone concentration, but artificial maintenance of high progesterone levels had no effect on the increase of mammary gland lactose at parturition. Mammary gland lactose concentrations in tammar wallabies are therefore a useful indicator of biosynthetic activity and as an index of lactogenesis but the role, if any, of progesterone withdrawal in lactogenesis remains unclear.

Identification of mesotocin, lysine vasopressin, and phenypressin in the eastern gray kangaroo (Macropus giganteus)

The neurohypophysial hormones of the eastern gray kangaroo (Macropus giganteus) have been isolated through molecular sieving and paper chromatoelectrophoresis. One oxytocin-like and two vasopressin-like peptides have been found. These peptides have been characterized by amino acid analysis. Mesotocin ([Ile8]-oxytocin), has been identified both by amino acid composition and by behavior in partition chromatography. Lysine vasopressin has been characterized by amino acid composition and by partial amino acid sequence determination. Phenypressin ([Phe2]-arginine vasopressin) has been identified by amino acid composition. Lysine vasopressin is about twice as abundant as phenypressin. These three peptides have previously been identified in two other macropodids, namely, the red kangaroo and the tammar wallaby, and seem to be present in all the family Macropodidae. The evolution of neurohypophysial hormones is discussed in regard to these results.

Glucose-6-phosphate dehydrogenase and lactate dehydrogenase activity in kangaroo and mouse oocytes

Glucose-6-phosphate dehydrogenase and lactate dehydrogenase activity in oocytes and follicle cells of the Australian marsupial, Macropus eugenii (the tammar), and the mouse were determined by a simplified microelectrophoresis method. Mouse oocytes have approx 285 times more G6PD activity per picolitre of cytoplasm than tammar oocytes and about 10 times more LDH. The ratio of LDH to G6PD in mouse follicle cells is close to 3 whereas in the tammar it approaches unity. The very low levels of activity of G6PD in tammar oocytes may be due to transcriptional, translational or metabolic differences compared with the mouse.

"Whey" proteins of milk of the red (Macropus rufus) and eastern grey (Macropus giganteus) kangaroo

1. A comparison is made of gel electrophoretic patterns of the "whey" proteins of the milk of red (Macropus rufus) and eastern grey (Macropus giganteus) kangaroos at various stages of lactation. Qualitative and quantitative changes occur with time during the mature phase of lactation of both types. Their onset is related solely to the stage of lactation. "Whey" proteins are isolated and characterised and the nature of protein changes determined for the first time. 2. The anodic electrophoretic pattern is divided into 6 main zones (designated A F in order of decreasing mobility) and 2 cathodic zones (G and H) that are only detected in the milk of M. giganteus. 3. Zones A, B and C are milk specific. Zone B is present throughout lactation in both species and is an alpha-lactalbumin. Zones A and C are present only in late lactation, zone C, usually, but not always, appearing first. Zone A is an alpha-lactalbumin in M. giganteus, but is not an alpha-lactalbumin in M. rufus. Zone C appears to be the same protein in both species and is possibly a beta-lactoglobulin. 4. Zone D is kangaroo serum albumin and zone E is possibly a beta 2-microglobulin. Zone F contains three main iron (III) binding bands whose relative intensity varies with stage of lactation. Their intensity differs from the corresponding blood serum transferrin bands. 5. Zone H of Macropus giganteus is a lysozyme. 6. Lactose is present in the milk, but is not the principal sugar. 7. The significance of the results is discussed.

Characterization and properties of a progesterone receptor in the uterus of the quokka (Setonix brachyurus)

A progesterone receptor system, with a high specificity for progestins, was detected in the uterine tissue of the marsupial, Setonix brachyurus (quokka), using the synthetic progestin 17 alpha, 21-dimethyl-19-nor-4,9-pregnadiene-3,20-dione (R5020). The apparent equilibrium dissociation constant of the ligand binding to the cytosolic component was 2.2 nmol/l, and to the nuclear component 4.8 nmol/l. Significant loss of binding ability of the receptor occurred when cytosol was pretreated with dextran-coated charcoal. All binding studies were performed, therefore, in the presence of endogenous steroid which was demonstrated to affect the dissociation constant but have no effect on the estimation of the concentration of binding sites. Cytosolic binding was increased sixfold by oestradiol-17 beta treatment in vivo, and the translocation of the bound complex into the nucleus was effected by progesterone. It is suggested that the binding component described plays a role in the action of progesterone on the uterine tissue of the quokka.

Macropodid marsupial testicular gonadotrophin receptors and their use in assays for marsupial gonadotrophins

The interactions of several mammalian follicle-stimulating hormones and luteinizing hormones with specific gonadotrophin receptors in macropodid marsupial testicular homogenates were investigated with a view to developing radioreceptor assays for marsupial FSH and LH. Testes from Eastern grey kangaroos and tammar wallabies possessed high affinity (dissociation constant congruent to 10(-10) mol/l) saturable receptor sites which were highly specific for LH or FSH. Luteinizing hormone receptor sites bound only highly purified LH preparations (human, ovine and rat) but did not bind highly purified FSH, TSH or prolactin while FSH receptor sites were equally specific for highly purified FSH preparations. These sites demonstrated a degree of species specificity in that marsupial pituitary extracts were relatively more potent in these assays than in assays using gonadotrophin receptors from rat testes. Serum from hypophysectomized female tammar wallabies had little effect on the slope and position of the LH standard curve but significantly depressed the dose-response curve for FSH. For this reason it was not possible to develop a radioreceptor assay for serum FSH using marsupial testicular FSH receptors. However, gonadotrophin receptors from both rat and marsupial testes have been employed in the successful development of radioreceptor assays for marsupial pituitary LH and FSH and marsupial serum LH.

Eastern grey kangaroo muscle creatine kinase

Creatine kinase has been purified to homogeneity from skeletal muscle of the eastern grey kangaroo, Macropus giganteus. The procedure included ethanol fractionation followed by chromatography on DEAE-cellulose. The enzyme had a molecular weight of approximately 86 000 with two subunits of 43 500. Two sulfhydryl groups were determined for the intact molecule and a further four on unfolding. Under standardized conditions, the metal ion specificity was determined as MgADP- greater than MnADP- greater than CoADP-, CaADP-; and the substrate specificity as MgADP- greater than MgdADP- greater than MgGDP- greater than MgXDP. Initial velocity and product-inhibition studies of the reverse reaction were consistent with a rapid random equilibrium reaction as observed for the rabbit muscle enzyme. However, initial-velocity studies in the forward reaction were consistent with a rapid equilibrium-ordered mechanism with MgATP2- binding before creatine. Preliminary studies on the binding of manganese nucleotides to the enzyme have been carried out using pulsed nuclear magnetic resonance to measure relaxation times of water protons.

Enzymes of galactose metabolism in livers of suckling and adult tammar wallabies (Macropus eugenii) and other marsupials

The activities of galactokinase, hexose-1-phosphate uridylyl transferase and UDPglucose 4-epimerase in homogenates of livers of two adult and 20 suckling tammar wallabies aged from 6 to 50 weeks were investigated. The activities of all three enzymes were high until 24-30 weeks post partum, after which they declined to low levels. The activities of the three liver enzymes were high in pouch young of six other species of marsupial. Comparison of the activities of the three liver enzymes in suckling tammar wallabies with those in suckling rats showed no difference between the two species in regard to galactokinase and uridylyl transferase, but the UDPglucose 4-epimerase activity in tammar wallabies was approximately double than found in rats. This may be related to the high galactose content of tammar wallaby milk compared with rat milk. In suckling tammar wallabies, the liver had higher enzyme activities than other tissues studied. It is concluded that, contrary to the suggestion of Stephens et al. (1975), pouch young marsupials are not deficient in their ability to metabolize galactose.

Mapping a marsupial X chromosome using kangaroo-mouse somatic cell hybrids

A series of marsupial-eutherian somatic cell hybrids was produced by fusion between lymphocytes from the red kangaroo (Macropus rufus) and HPRT-deficient mouse cells. The hybrids lost marsupial chromosomes and could therefore be used to map marsupial genes. Several of the hybrids contained a complete red kangaroo X chromosome and expressed the kangaroo form of the enzymes HPRT, G6PD, and PGKA. A number of HPRT-deficient revertant cell lines were derived from the hybrids. These possessed a variety of partially deleted X chromosomes. With these cell lines, it has been possible to establish the X-linkage of the genes for HPRT, G6PD, and PGKA in this marsupial and to localize these three genes to the terminal portion of the euchromatic arm of the red kangaroo X chromosome.

Steroid metabolism in the yolk sac placenta and endometrium of the tammar wallaby, Macropus eugenii

Yolk sac and endometrial tissue were obtained from tammar wallabies between 11 and 25 days after the removal of pouch young. Tissues were examined histologically and steroid-metabolizing enzymes were identified by incubation for 3 h at 37 degrees C in Medium 199 containing labelled steroid precursors. Yolk sac membrane (YSM) incubated with labelled pregnenolone produced a small amount of progesterone and pregnanediols; 80.5 +/- 8.4 (S.E.M.) % of the original substrate remained unmetabolized. Labelled androstenedione was metabolized to 5 alpha-androstane-3,17-dione and androsterone, and only 5.8 +/- 3.8% of the original substrate remained at the end of incubation. Incorporation of androstenedione or dehydroepiandrosterone (DHA) into phenolic compounds was low (0.5 +/- 0.1%). There was no evidence for the enzymes, arylsulphatase or sulphotransferase, in YSM. Endometrial tissue from the same animals metabolized pregnenolone, DHA and androstenedione, converted progesterone to androstenedione, and produced aqueous-soluble steroid conjugates. The results demonstrated that YSM contains enzymes associated predominantly with steroid catabolism and with incipient progesterone synthesis. The findings are discussed in relation to the histological appearance of the tissues and compared with placental steroid synthesis in eutherian mammals.

Prolactin receptors in the mammary gland, corpus luteum and other tissues of the tammar wallaby, Macropus eugenii

Specific binding of radio-iodinated ovine prolactin to subcellular tissue fractions of the tammar wallaby (Macropus eugenii) was investigated. Specific binding was found, in order of decreasing binding activity, in the lactating mammary gland, corpus luteum, corpus albicans, adrenal gland and ovary. Specific binding was absent in kidney, liver, brain and inactive mammary gland. The mean association constant (Ka at 23 degrees C) was determined as 0.90 x 10(9), 2.20 x 10(9), 2.44 x 10(9), 3.38 x 10(9) and 10.98 x 10(9) l/mol for mammary gland, adrenal, corpus albicans, corpus luteum and ovary respectively. The mean receptor concentration (N) varied from 92.87 x 10(-14) mol/mg protein for the mammary gland to 1.03 x 10(-14) mol/mg protein for the ovary. The concentration in the corpus luteum varied between tissue pools collected at different times of the annual breeding cycle. The specificity for prolactin was shown in the mammary gland and corpus luteum by the failure of ovine FSH, LH, GH and TSH to displace 125I-labelled ovine prolactin, whereas it was displaced readily by both ovine and bovine prolactin.

Growth of the corpus luteum and its progesterone content during pregnancy in the tammar wallaby, Macropus eugenii

Corpora lutea were obtained from wallabies at different stages of pregnancy, following removal of pouch young to initiate embryonic development. Progesterone was present at a concentration of 11.3 ng/mg in quiescent corpora lutea from lactating animals. Progesterone values rose with increasing corpus luteum weight to reach a maximum of 40--50 ng/mg in corpora lutea weighing 50--60 mg. Total progesterone reached a maximum of 1500 +/- 300 (s.e.m.) ng at Days 21--23 after removal of pouch young, but fell markedly at Days 24 and 25 (900 +/- 150 ng) immediately before parturition.

Red cell metabolism in red and grey kangaroos

Glucose utilization, lactate production and glutathione regeneration were measured in the red blood cells of 2 species of Australian Marsupials, Eastern grey Kangaroo (Macropus gigantus) and red kangaroo (Macropus rufus), and were found to be significantly lower in the red blood cells from grey than that of red kangaroos.

Temperature regulation and oxygen consumption in the developing macropod marsupial Setonix brachyurus

1. When kept at ambient temperatures of 17-5 and 24 degrees C the colonic temperatures of joeys younger than 166 days declined to near ambient temperature. Pouch joeys of 166 days and older were however able to maintain their colonic temperatures at about 35 degrees C. 2. Joeys first developed the ability to sustain high O2 consumption rates in response to cooling, when aged between 144 and 169 days. Only when this latter facility was fully developed in ontogeny could body temperature be maintained in a cool environment. 3. When joeys older than 130 days were kept in a metabolism chamber at pouch temperature (37-5 degrees C) and at high humidity their body temperatures quickly rose to lethal levels, demonstrating the need for cooling mechanisms whilst still contained within the pouch.

The regulation of gluconeogenesis in pouch young of the tammar wallaby, Macropus eugenii (Desmarest)

Parenchymal cells have been prepared from wallaby pouch-young liver by enzymic means. Such cells exclude Trypan blue, lose little lactate dehydrogenase into the incubation medium, have an adenylate energy charge of about 0'75 and increase production of glucose from endogenous sources in the presence of 1O-9M glucagon. We conclude that the cells are metabolically viable. Hepatocytes isolated from fed pouch young released glucose in the absence of added substrates'. The rate of glucose release was increased when L-Iactate, L-Iactate+ pyruvate, propionate or fructose were added. After 24 h without food, glucose release in the absence of substrate was greatly reduced but the effect of substrate addition was greater with all substrates other than fructose.