Human Reproduction, Vol 12, 1037-1042, Copyright © 1997 by Oxford University Press
U Ottander, M Nakata, T Backstrom, K Liu, T Ny and JI Olofsson
The relationship was investigated between different ultrasonographically
defined subtypes of the human corpus luteum and progesterone production.
Twenty-one women in the mid-luteal phase who underwent laparotomy for
benign uterine conditions volunteered for this study. The corpus luteum was
identified by preoperative ultrasound and classified into four types
according to earlier established criteria, where types a and c were
centrally hypoechoic, types b and d were centrally echogenic, types a and b
had thin surrounding 'walls' (<3 mm) and types c and d had thick walls
(<3 mm). After luteectomy, the theca externa capsule was removed and
tissue from directly beneath the surface ('peripheral region') and the
layer immediately beneath ('inner region') minced into 4-6 mg pieces.
Following preincubation, pieces were incubated for 3 h at 37 degrees C in
HEPES-minimal essential medium buffer with or without human chorionic
gonadotrophin (HCG; 10 IU/ml), and subsequently progesterone accumulation
in the medium was determined by radioimmunoassay. The highest progesterone
production was consistently seen in the peripheral region. Type a had a
significantly (P > 0.01) lower progesterone production (3.2 +/- 1.5
nmol/g tissue wet weight, mean +/- SEM, n = 4) than that of types b, c and
d (17.7 +/- 3.5 nmol/g tissue wet weight, n = 9). All types responded to
HCG with an almost two-fold increase in progesterone production. However,
the maximal progesterone produced following stimulation by HCG in the type
a corpus luteum was <50% of the basal (unstimulated) progesterone
synthesis of any other type of corpus luteum. Using in-situ hybridization,
with a primate RNA probe complementary to the region coding the
extracellular part of the luteinizing hormone (LH) receptor, a highly
localized expression of LH receptor mRNA to the peripheral region was
found. Negligible or low levels of expression were found in the theca
externa capsule and the inner region. No obvious correlations between the
different subtypes of corpora lutea and LH receptor mRNA expression were
seen. Thus, the ultrasonographic detection of a thin- walled and centrally
hypoechoic corpus luteum correlates well with reduced progesterone
secretion. The underlying cellular mechanism does not appear to involve a
diminished sensitivity to the gonadotrophic stimulation by LH or HCG.
ARTICLES
Compartmentalization of human chorionic gonadotrophin sensitivity and luteinizing hormone receptor mRNA in different subtypes of the human corpus luteum
Department of Obstetrics and Gynecology, Umea University Hospital, Sweden.
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