Muscarinic effects and foetal cardiovascular and hormonal responses in utero.
BACKGROUND
Cholinergic mechanisms play an important role in the control of hormonal and vascular regulation. However, in utero development of cholinergic regulation in the foetal hormonal systems is not clearly understood.This study investigated foetal hormonal and cardiovascular responses following application of the muscarinic antagonist atropine.


METHODS
Chronically prepared near-term ovine foetuses (control and experimental: n=5, each group) were used. After 4-5 days' surgical recovery, conscious ewes and their foetuses were tested in vivo.


RESULTS
In response to intravenous atropine, foetal systolic, diastolic, and mean arterial pressure, as well as heart rate, increased immediately. Inhibition of muscarinic systems in the circulation caused a reduction of plasma angiotensin II levels, while angiotensin I in the circulation remained unchanged in the foetus. In addition, foetal plasma aldosterone levels were significantly increased following blockade of the cholinergic receptor, while other hormones, including arginine vasopressin, adrenocorticotrophic hormone, and atrial natriuretic peptide, were not changed in foetal blood under the same condition.


CONCLUSIONS
The results suggest that foetal automatic systems, not those hormonal factors tested, play a major role in cholinergic mechanisms mediating cardiovascular control. Furthermore, the data provide new information on how muscarinic inhibition affects renin-angiotensin system and adrenal cortex functions. Key words: aldosterone, angiotensin-converting enzyme, autonomic regulation, foetus.
Jianli Zheng
Perinatal Biology Centre, Soochow University School of Medicine, Suzhou 215123, People's Republic of China.
Weili Yang
Li Cao
Shigang Li
Yuying Zhang
Zhen Wan
Caiping Mao
D000450:Aldosterone / Q000097:blood; D000803:Angiotensin I / Q000097:blood; D000804:Angiotensin II / Q000097:blood; D000818:Animals; D001127:Arginine Vasopressin / Q000097:blood; D001285:Atropine / Q000008:administration & dosage / Q000494:pharmacology; D001681:Biological Assay; D001794:Blood Pressure / Q000187:drug effects; D002319:Cardiovascular System / Q000187:drug effects* / Q000378:metabolism*; D005260:Female; D005333:Fetus / Q000187:drug effects* / Q000378:metabolism*; D006339:Heart Rate / Q000187:drug effects; D006728:Hormones / Q000097:blood*; D007262:Infusions, Intravenous; D018727:Muscarinic Antagonists / Q000494:pharmacology*; D011247:Pregnancy; D012756:Sheep
D006728:Hormones; D018727:Muscarinic Antagonists; D000804:Angiotensin II; D001127:Arginine Vasopressin; D000450:Aldosterone; D001285:Atropine; D000803:Angiotensin I