The metabolic clearance of progesterone in the pregnant rat: Absence of a physiological role for the lung

Journal Article · Thu Jun 01 00:00:00 EDT 1989 · Biology of Reproduction; (USA)

DOI:https://doi.org/10.1095/biolreprod40.6.1188· OSTI ID:5471446

Waddell, B J; Bruce, N W ^[1]

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1. Univ. of Western Australia, Nedlands

The metabolic clearance rate (MCR) of progesterone is among the highest for all steroid hormones studied, yet it is difficult to apportion this high MCR to specific organ contributions. The isolated lung has been shown to metabolize progesterone, and since this tissue receives the entire cardiac output, potentially it could make a major contribution to the overall MCR. This possibility was examined in the present study by measuring lung extraction of (3H)progesterone under steady-state conditions in the intact pregnant rat. Anesthetized rats (n = 6) were infused with (3H)progesterone via a femoral vein for 100 min on Day 16 of pregnancy. After the onset of steady state (40 min), four blood samples were obtained at 20-min intervals from the right ventricle and from the aorta, and the concentrations of (3H)progesterone and its metabolites were determined. Throughout the sampling period, mean arterial pressure and heart rate remained stable (two-way analysis of variance), as did the production rate (3.76 +/- 0.35 mg/day; mean +/- SEM) and the MCR (34.8 +/- 3.5 ml/min) of progesterone. Despite this high rate of clearance, there was no difference between the concentration of (3H)progesterone in arterial and right ventricular blood, indicating no net extraction of progesterone during passage through the lung. Furthermore, there was no change in the concentration of either lipid-soluble or aqueous-soluble (3H)progesterone metabolites during trans-lung passage. These observations demonstrate that the lung does not contribute to the MCR of progesterone when measured under physiological and steady-state conditions. Therefore, the relationship, MCR (ml/min) = whole-body extraction (%) x cardiac output (ml/min), is upheld for progesterone in the rat.

• OSTI ID: 5471446
• Journal Information: Biology of Reproduction; (USA), Vol. 40:6; ISSN 0006-3363
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
PROGESTERONE
METABOLISM
LUNGS
METABOLITES
PREGNANCY
RATS
STEADY-STATE CONDITIONS
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ANIMALS
BODY
HORMONES
HYDROGEN COMPOUNDS
ISOTOPE APPLICATIONS
KETONES
MAMMALS
ORGANIC COMPOUNDS
ORGANS
PREGNANES
RESPIRATORY SYSTEM
RODENTS
STEROID HORMONES
STEROIDS
VERTEBRATES
550501* - Metabolism- Tracer Techniques