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P. O. JANSON and P. SVENDSEN

Department of Physiology, University of Göteborg, and Department of Obstetrics and Gynaecology and Roentgen Department II, Sahlgren's Hospital, Göteborg, Sweden

(Received 18th July 1974)

Hysterectomy is known to increase the life-span of the CL in several mammalian species (Dobrowolski & Hafez, 1971; Anderson, 1973) and the involvement of prostaglandins has been suggested (Pharriss, 1970; McCracken, Baird & Goding, 1971). Total hysterectomy in the rabbit extends the life of the CL (Asdell & Hammond, 1933) and exogenous prostaglandins cause luteolysis (Duncan & Pharriss, 1970). Few detailed studies have been reported on the vasculature of the rabbit ovary and the present investigation was carried out to determine whether anatomical prerequisites exist for a local uterine control of luteal function.

Two groups of female albino Swedish Land rabbits, 5 to 6 months old and weighing 2·3 to 3·0 kg, were studied. The first group (four animals) consisted of untreated animals that had not

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J.-E. Damber and P. O. Janson

Summary. Testicular blood flow was measured by a radioactive microsphere technique. A significant correlation, r s = 0·82, was found between testicular blood flow and testosterone outflow in the spermatic venous blood, indicating that factors which affect the testicular circulation may influence testicular endocrine function.

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G. Selstam, P. O. Janson and S. Eden

Summary.

After perfusion of 10 rabbit ovaries in vitro with a modified Krebs bicarbonate buffer containing dextran and glucose, the concentration of cAMP in the perfusion medium was significantly increased 2·5 min after stimulation with 10 μg LH/ml medium and was higher at 15 and 30 min. Intravenous injection of 100 μg LH/rabbit caused a significant increase of cAMP concentrations in the ovarian venous blood from 8 ovaries 10 min after the injection and the cAMP concentrations were higher after 15 and 30 min. The ovarian blood flow was not changed after the LH injection. It is concluded that perfusion techniques can be useful in analysis of the mechanisms and physiological significance of release of cAMP from the ovary after hormonal stimulation.

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K. AHRÉN, P. O. JANSON and G. SELSTAM

Summary.

A technique for perfusion of the rabbit ovary in vivo is described which allows a quantitative determination of the intra-ovarian passage from artery to vein of 15 ± 5 μm non-radioactive microspheres. The passage of microspheres was less than 1 % in ovaries containing follicles (from non-pregnant rabbits) as well as in ovaries containing CL (from rabbits in different stages of pseudopregnancy). Addition of a vasodilator to the perfusion system did not influence the result.

The present results do not indicate that arterio-venous shunts of physiological significance exist in the rabbit ovary.

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A. Bendz, N. Einer-Jensen, O. Lundgren and P. O. Janson

Summary. A miniature Geiger—Müller probe was inserted into one ovary of 8 women undergoing hysterectomy. A control probe was inserted into the other ovary of 2 of the women. Krypton-85 in 0·15 m-NaCl was infused into the adjacent utero-ovarian vein and the radioactivity was registered for 5–14 min after the infusion. An increase of radioactivity was recorded in the ovary in 5 cases. In one of the women with 2 probes, no increase in radioactivity was observed in the control ovary. The results show a local transfer of gas from the ovarian branch of the uterine vein into the adjacent ovary, which may be due to a countercurrent exchange mechanism between the vessels of the human uterine adnexa.

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P. V. Holmes, J. Sogn, E. Schillinger and P. O. Janson

Summary. Rabbit ovaries were isolated surgically before the ovulatory gonadotrophin stimulation and perfused in vitro. Untreated, control ovaries never ovulated. Ovaries treated in vitro with ovine LH ovulated 10–14 h later and the oocytes had undergone germinal vesicle breakdown (GVB). LH induced increases in progesterone secretion from the treated ovaries. A 3β-hydroxysteroid dehydrogenase blocker ('Compound A') effectively reduced progesterone secretion into the perfusate and follicular fluid to very low levels but had no effect on ovulation rate or on oocyte maturation. Excessively high progesterone levels were obtained artificially in perfusates by addition of exogenous steroid; the number of ovaries ovulating was markedly reduced but there was no effect on oocyte maturation.

It is concluded that the rise in progesterone that normally occurs immediately after the LH surge is not a prerequisite for ovulation in the rabbit. However, progesterone may have a modifying effect on LH-induced follicle rupture when at a pharmacologically high level.

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P. O. Janson, J.-E. Damber and C. Axén

Summary. Ovarian and luteal blood flow rates were measured, by means of radioactive microspheres, in anaesthetized rabbits on Day 8 of pseudopregnancy before and after lowering the ovarian perfusion pressure with a sling placed around the aorta. When blood pressure was lowered by 42% luteal flow decreased 9-fold whilst flow to the remaining part of the ovary remained unchanged, indicating the presence of an autoregulatory mechanism in the ovarian interstitital gland.

Ovarian progesterone secretion, assessed from progesterone concentrations in ovarian venous blood, was positively correlated to the blood flow per unit of weight of luteal tissue. These data indicate that a high rate of luteal blood flow may be necessary for an optimal steroid production by the corpus luteum.

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M. Brännström, B. M. Boberg, J. Törnell, P. O. Janson and K. Ahrén

Summary. The effects of two different protein synthesis inhibitors (cycloheximide and puromycin) on the ovulatory process were examined in vitro using a perfused rat ovary model. Ovaries of PMSG (20i.u.)-primed rats were perfused for 21 h. Release of cyclic adenosine 3′,5′-monophosphate (cAMP) and steroids (progesterone, testosterone, and oestradiol) was measured and the number of ovulations was estimated by counting released oocytes. Unstimulated control ovaries did not ovulate whereas addition of LH (0·1 μg/ml) plus 3-isobutyl-1-methylxanthine (IBMX; 0·2 mm) resulted in 16·7 ± 3·5 ovulations per treated ovary. Cycloheximide (5 μg/ml) totally inhibited the ovulatory effect of LH + IBMX when present from the beginning of the perfusions and also when added 8 h after LH + IBMX. No inhibition was seen when cycloheximide was added 10 h after LH + IBMX (1–1·5 h before the first ovulation; 15·2 ± 4·4 ovulations per treated ovary). Puromycin (200 μg/ml) completely blocked ovulation when present from the beginning of the perfusions and the inhibition was ≃60% (6·5 ± 2·2 ovulations per treated ovary) when the compound was added 8 h after LH + IBMX. Both inhibitors increased LH + IBMX-stimulated cAMP release substantially, but decreased the release of progesterone, testosterone and oestradiol. These results indicate that de-novo protein synthesis is important late in the ovulatory process for follicular rupture to occur.

Keywords: cycloheximide; ovulation; perfusion; protein synthesis; puromycin; rat