Continuous measurement of blood gas tensions in the fetal guinea pig by mass spectrometry.
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Animals↗
Biomedical subjects
A M Carter
Publications and source records attributed to A M Carter.
Effect of noradrenaline on circulation in the genital tract of early and late pregnant guinea-pigs.
Noradrenaline infusions were given to anaesthetized guinea-pigs in early (19--23 days) and near-term (61--66 days) pregnancy. Radioactive microspheres (15 micrometers) were used to determine blood flow in various regions of the genital tract. In late gestation, a 10-min intravenous infusion of 1 micrograms noradrenaline/min/kg elicited moderate increases in vascular resistance that were counteracted by the pressor response. Uterine and placental blood flow remained unchanged, although there was a 27% decrease in perfusion of the uterine cervix and a fall of 19% in vaginal blood flow. In early pregnant guinea-pigs, blood pressure rose but vascular resistance was unaffected, resulting in an augmentation of placental blood flow. During infusion of 10 micrograms noradrenaline/min/kg, the vasonconstrictor response in late pregnancy was accentuated, and a strong decrease in tissue perfusion was noted in the placenta (-36%), uterine horns (-39%), cervix (-70%) and vagina (-56%). At the higher rate of noradrenaline infusion, vascular resistance also increased in the genital tract of early pregnant animals, although to a lesser extent than in late pregnancy. The results indicate an enhancement of the vasoconstrictor response to circulating catecholamines in near-term pregnancy.
Animals↗
Blood gas tensions and acid-base status in the fetal guinea-pig.
To establish reference values for blood gas tensions in the fetal guinea-pig, blood was obtained by cardiac puncture or by puncture of the umbilical vein and analysed for pH, PCO2, PO2, haemoglobin concentration (Hb), oxyhaemoglobin saturation (SO2), and packed red cell volume. The measurements were made near term of pregnancy, on the 61st-66th day, and the dams were anaesthetized with diazepam and sodium pentobarbitone. In the umbilical venous blood, mean values for pH, PCO2, PO2, Hb and SO2, respectively, were 7.324, 45.1 mmHg, 29.5 mmHg, 8.8 mmol 1(-1), and 0.57 mol O2 per mol of haemoglobin monomer. The corresponding values for arterial blood from the heart were 7.265, 53.4 mmHg, 18.6 mmHg, 9.2 mmol 1(-1) and 0.25. Thus, blood gas tensions in the fetal guinea-pig are much closer to those of fetal primates and ungulates than has been recognized previously.
Acid-Base Equilibrium↗
Increased myometrial blood flow evoked by vasoactive intestinal polypeptide in the non-pregnant goat.
1. The effect of vasoactive intestinal polypeptide (VIP) on myometrial blood flow was evaluated in anaesthetized goats. A solution of VIP, or vehicle alone, was infused into the right internal iliac artery for a period of 10 min. The myometrial blood flow in both uterine horns was measured from the third to the seventh min of the infusion by the gas clearance technique after local injection of (133)xenon in 10 mul. saline solution. Blood samples were collected from both utero-ovarian veins 5 min from the onset of the infusion and the plasma concentration of VIP determined by radio-immunoassay.2. During infusion of vehicle before VIP, myometrial blood flow was of the same magnitude in both uterine horns, i.e. 0.06-0.12 ml./min per g. The blood flow of the right horn increased to 0.20-0.39 ml./min per g during infusion of VIP (300 p-mole/min) in the ipsilateral artery, whilst that of the left horn rose to 0.13-0.26 ml./min per g. The effect was sometimes observed to last for more than 40 min.3. Increased myometrial blood flow was observed with infusion rates down to 3 p-mole/min. Once a response to VIP had been provoked, however, the vasculature sometimes became refractory to further stimulation.4. The plasma concentration of VIP increased in both utero-ovarian veins during unilateral infusion of the peptide.5. Methylene blue given through the infusion catheter stained tissue in both uterine horns, further evidencing that their blood supply is not entirely separate.6. Uterine motility was observed to diminish during the VIP infusions.7. During infusion of VIP (300 p-mole/min) heart rate rose from 146 +/- 6 to 158 +/- 7 beats/min. No significant change occurred in arterial blood pressure.8. It is concluded that the increase in blood flow is due to a local response and that, since VIP has been demonstrated in uterine nerve endings, it may act as a neuro-transmitter mediating vasodilatation in the uterus.
Animals↗
Effects of VIP in the female genital tract.
Vasoactive Intestinal Polypeptide (VIP) has been demonstrated in the female genitourinary tract, localized in neurons which seem to innervate vessels and non-vascular smooth muscle. The present work has demonstrated that the concentration of immunoreactive VIP varies between different mammalian species and within the genital tract of the same species. Using various in vivo and in vitro preparations the peptide was found to have a dose-dependent inhibitory effect on the myoelectrical activity and contractility of the uterine muscle, and to increase myometrial blood flow. The findings support the hypothesis that VIP may play a physiological role in the local control of uterine motility and blood flow.
Animals↗
Adrenergic and cholinergic responses in the uteroplacental vascular bed of the guinea pig.
The effects on uterine and maternal placental circulation of adrenergic and cholinergic drugs, injected selectively in the ovarian and uterine arteries of guinea pigs, were analysed by serial angiography. Noradrenaline, 0.5 nmol/kg, was found to cause a reduction in both ovarian and uterine blood flow, associated with arterial vasoconstriction and impairment of the placental circulation. This response could be prevented by alpha-adrenergic blockade with 25 nmol/kg phenoxybenzamine. At injection into the ovarian artery, phenoxybenzamine alone increased ovarian blood flow and elicited arterial vasodilatation. At injection into the uterine artery the response was more variable, but vasodilatation was observed in four animals of six. Acetylcholine, 0.5 to 5.0 nmol/kg, evoked an increase in both ovarian and uterine blood flow and arterial vasodilatation. When the dose was increased to 50 nmol/kg, dilatation of the extrinsic uterine arteries was maintained, but the placental circulation was reduced due to concomitant contraction of the myometrium. All the effects of acetylcholine could be blocked by prior administration of 10 nmol/kg atropine. This dose of atropine did not affect uterine or placental circulation when given alone.
Acetylcholine↗
Myoendothelial and placental blood flow responses to ritodrine infusion in the guinea pig.
The effect of ritodrine hydrochloride on uterine blood flow was investigated in near-term guinea pigs. The infusion of ritodrine in doses sufficient to inhibit uterine activity provoked tachycardia, and the cardiac output tended to rise. The percentage of cardiac output reaching the gravid uterus did not alter during the infusion of 12 micrograms per minute of ritodrine but decreased from 12% to 10% when the infusion rate was 120 micrograms per minute. There was an increase in the myoendothelial fraction of cardiac output in both instances, whereas the placental fraction decreased at the higher rate of infusion. Perfusion of the myoendothelial tissue improved during the infusion of 12 or 120 micrograms per minute of ritodrine, increasing by 25% and 18% respectively. No significant alteration occurred in the perfusion of the placental tissue.
Animals↗
Regional blood flow measurements with 15 micron and 50 micron microspheres in pregnant guinea-pigs.
Two sizes of microsphere were used to determine regional blood flow in pregnant guinea-pigs. Tissue perfusion measured with 50 micron microspheres was significantly greater than that measured with 15 micron microspheres in the small intestine, uterus, vagina, and placenta. A significantly larger proportion of the smaller microspheres passed through the systemic vasculature and could be detected in the lungs.
Animals↗
Effect of terbutaline sulphate on ovarian, uterine and maternal placental blood flow in the anesthetized guinea pig.
The effect of terbutaline sulphage, a beta-adrenergic agonist, on uteroplacental blood flow was studied in the guinea pig during late pregnancy. Organ blood flows and cardiac output were assessed by the radioactive microsphere technique. Infusion of terbutaline at a rate of 2nmol min-1 kg-1 body weight caused a significant increase in cardiac output and in the perfusion of the uterus and ovaries, but there was no significant alteration in maternal placental blood flow. When the infusion rate was increased tenfold, there was also a significant rise in the blood supply to the bronchi, urinary bladder, kidneys, and adrenal glands. Maternal placental blood flow was not adversely affected even by this large dose of the drug, although there was a significant reduction in the placental share of the cardiac output.
Anesthesia↗
Actions of a new vasopressin analogue (1-deamino-6-carba-[8-arginine]-vasopressin) on regional blood flow in pregnant guinea pigs.
Regional blood flow responses to 1-deamino-6-carba-(8-arginine)-vasopressin (dCAVP) were investigated in pregnant guinea pigs by the radioactive microsphere technique. Intravenous injection of 0.1 microgram/kg body weight caused a moderate rise in mean arterial blood pressure from 6.8 to 7.9 kPa, a significant reduction in tissue perfusion of the stomach, mammary gland, urinary bladder and vagina, and a significant increase in renal and cerebral blood flow. In a small number of animals given 1.0 microgram/kg of dCAVP, which evoked a strong pressor response, it was also possible to demonstrate a reduction in cutaneous and pancreatic blood flow and an augmentation of adrenal blood flow. Uterine and maternal placental blood flow did not alter significantly following administration of this vasopressin analogue.
Animals↗
Effect of 1-deamino-6-carba- (8-arginine)- vasopressin on organ blood flow in the female guinea pig.
An analogue of (8-arginine)-vasopressin, characterized by removal of the Nalpha-amino group and replacement of the disulphide bridge with a thioether bridge (dCAVP), was found to increase blood flow to the brain, kidneys and adrenal glands of female guinea pigs whilst decreasing perfusion of the skin and skeletal muscle. An increase was noted in the proportion of 15 micrometer microspheres trapped in the spleen, probably contingent upon reduced arteriole-venous shunting. These responses were obtained both at estrus and during the luteal phase of the estrous cycle. In contrast, uterine and vaginal blood flows showed a significant reduction only during the luteal phase.
Animals↗
Circulatory adjustments to pregnancy in the rabbit.
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Animals↗
Blood flow to the genital tract of oestrous and dioestrous guinea-pigs.
Ovarian, uterine and vaginal blood flow were determined in 22 virgin guinea-pigs by the tracer microsphere technique. Measurements were made during oestrus, when cornified cells appeared in the vaginal smear (Day 1), or during the luteal phase of the cycle (Day 11). The total rate of blood flow to the genital tract was 0-58 ml.min-1 on Day 11 and 2-92 ml.min-1 on Day 1. This difference was largely due to an 8-fold increase in uterine blood flow from 0-26 to 2-01 ml.min-1. Although uterine weight increased over the same period, there was a significant increase in uterine tissue perfusion from 0-32 to 1-18 ml.min-1.g-1. The vagina exhibited a similar pattern, including a significant increase in tissue perfusion. Ovarian blood flow decreased from a value of 0-19 ml.min-1 during the luteal phase to 0-10 ml.min-1 at oestrus. Perfusion of the ovarian tissue was considerably greater on Day 11 than on Day 1 (2-86 versus 1-39 ml.min-1.g-1).
Animals↗
Effect of a vasopressin analogue (Nalpha-glycyl-glycyl-glycyl-[8-lysine]-vasopressin) on organ blood flow in the pregnant guinea pig.
Nalpha-triglycyl-(8-lysine)-vasopressin (TGLVP) was administered intravenously to pregnant guinea pigs and the effect on regional blood flow examined by the radioactive microsphere technique. A dose of 10 mug/kg TGLVP caused an elevation of the mean arterial blood pressure, from 6.4 to 11.1 kPa, a significant reduction in blood flow to the gut, skin and skeletal muscle and a significant increase in blood flow to the spleen. The number of 15 +/- 5 mum microspheres reaching the lungs diminished significantly after 10 mug/kg TGLVP, indicating that this dose constricted arterio-venous short circuits in the systemic circulation. There was also a decrease in blood flow to the urogenital tract, including the placentae. When 3 mug/kg TGLVP was injected, the mean arterial blood pressure rose from 6.5 to 8.7 kPa and there was no longer any consistent effect on maternal placental blood flow. It is suggested that pregnancy constitutes a contraindication for TGLVP, since a reduction in uterine and maternal placental blood flow might occur with clinically relevant doses.
Animals↗
Ionic composition and cardiotoxicity of dimeric contrast media at injection into the coronary arteries of rabbits.
The relation between ionic composition and cardiotoxicity of two dimers, iocarmate and iozomate, was investigated by selective injection into the left and right coronary arteries, Least toxic reactions developed at a sodium concentration of 263 to 315 mmol/l for sodium-meglumine iocarmate and 271 to 379 mmol/l for sodium-meglumine iozomate.
Animals↗
A technique for monitoring endometrial or decidual blood flow with an intra-uterine thermistor probe.
A technique is described for studying endometrial or decidual blood flow by introducing a thermistor, mounted in a flexible catheter, into the uterus. The technique was first tested in model experiments and in the pregnant rabbit and was then used to study the blood flow of the human uterus. In pregnant women, the thermistor was introduced between the decidua and fetal membranes, and in non-pregnant women, it was applied to the endometrium of the fundus. Intra-uterine pressure was recorded simultaneously. No complications were encountered in either pregnant or non-pregnant patients. Decidual or endometrial blood flow remained steady over long periods. There were transient fluctuations about the mean level, usually associated with myometrial contractions, but these could easily be distinguished from changes in the level of blood flow evoked by administration of vasoactive drugs.
Animals↗
Uterine, maternal placental and ovarian blood flow throughout pregnancy in the guinea pig.
The blood flow to the placenta, uterus, ovaries, and vagina was measured with the aid of radioactive microspheres in thirty pregnant guinea pigs between 22 and 66 days of gestation. The rise in maternal placental blood flow during gestation was ascribable both to an increase in the extent of the vascular bed and to an improvement in relative blood flow from 0.77 ml X min-1 X g-1 at 26--35 days to 1.53 ml X min-1 X g-1 at 56--65 days. The relative rate of blood flow to the subplacenta was constant during the period studied (0.15 ml X min-1 X g-1), although its fraction of total placental blood flow decreased from 10% at 26--35 days to scarcely 1% at 56--65 days. The percentage of total placental weight attributable to the subplacenta during these intervals was 50% and 10% respectively. Perfusion of the uterine tissue decreased during gestation from 0.32 ml X min-1 X g-1 at 26--35 days to 0.18 ml X min-1 X g-1 at 56--65 days. A relation was observed between the weight of and blood flow to an uterine horn and the weight of its contents. Between 22 and 55 days of gestation, ovarian blood flow was related to the number of fetuses in the ipsilateral horn and, in seven unilateral pregnancies, there was a significant difference between the ovarian blood flows on the gravid and non-gravid sides. After day 55 no relation between the ovarian blood flows and the number of fetuses in the ipsilateral horn could be found.
Animals↗
Uterine and placental circulation in the guinea-pig: an angiographic study.
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Angiography↗