# Platelet-Activating Factor does not stimulate the in vitro contractile activity of the pregnant sheep myometrium near term

Rafael Garcia Villar, J E Parks, S R Hough, Peter W Nathanielsz

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## To cite this version:

Rafael Garcia Villar, J E Parks, S R Hough, Peter W Nathanielsz. Platelet-Activating Factor does not stimulate the in vitro contractile activity of the pregnant sheep myometrium near term. 41st Annual Scientific Meeting of the Society for Gynecologic Investigation of the, Mar 1994, Chicago, Illinois, United States. **hal-01601015**

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SOCIETY FOR GYNECOLOGIC INVESTIGATION
ABSTRACT FORM

Office Use Only:

ID# Abst# 41st Annual Scientific Meeting

Date Rec'd MARCH 22.25, 1994

CHICAGO, IL Abstract 010

DO NOT FOLD ABSTRACT FORM

### PLATELET-ACTIVATING FACTOR DOES NOT STIMULATE THE IN VITRO CONTRACTILE ACTIVITY OF THE PREGNANT SHEEP MYOMETRIUM NEAR TERM

Garcia-Villar, R.*, Parks, J.E.¹*, Hough, S.R.* and Nathanielsz, P.W. Laboratory for Pregnancy and Newborn Research, College of Veterinary Medicine and Department of Animal Science, Cornell University, Ithaca, NY 14853-6401 HD 21350.

**AIM OF THE STUDY:** In women and several animal species platelet-activating factor (PAF) has been reported to stimulate myometrial contractility thus contributing to parturition. The sheep has been extensively investigated to study control of myometrial activity at different stages of pregnancy. There are no data on the effects of PAF on myometrial contractility either in vivo, or in vitro, in this important experimental species. The present study was aimed at determining the effects of PAF on uterine muscle strips from pregnant sheep in vitro.

**METHODS:** Strips of uterine muscle (0.4 x 0.8 mm) from seven sheep at 120-145 days gestation age were superfused in vitro with 37°C oxygenated Krebs buffer, with or without 3 µM indomethacin. Contractions were recorded with strain gauges under a resting tension of 1 g and automatically quantified. Cumulative concentration-response curves (CRCs) to PAF (0.01 mM to 1 µM), oxytocin (4.2 pM to 42 nM) and prostaglandin (PG)F<sub>2α</sub> (1 nM to 100 µM) were constructed using duplicate data points for each drug concentration in each animal. Wherever possible EC50 values were calculated. PAF superfusion effluents were collected for a bioassay of PAF based on [³H]serotonin release for equine platelets.

**RESULTS:** All myometrial strips displayed a regular pattern of spontaneous contractions about 1 min duration at 2-3 min intervals. As expected, both oxytocin and PGF<sub>2α</sub> consistently stimulated myometrial activity in a concentration-related fashion. The EC50 value for PGF<sub>2α</sub> (19 nM) was significantly (p < 0.01) lower than that for oxytocin (0.18 nM). In contrast, despite a wide range of concentrations and different experimental conditions, which included synthetic PAF (1-O-hexadecyl and 1-O-octadecyl, Sigma) with and without 2.5% BSA and HPLC-purified PAF from bovine sperm, PAF was without effect on myometrial contractility in any of the tissue preparations. Bioassay of superfusion effluents demonstrated that PAF remained biologically active during the course of the experiment.

**CONCLUSION:** Our results indicate that in-vitro muscle strips from late-pregnant sheep myometrium which are dose-dependently contracted by both PGF<sub>2α</sub> and oxytocin, are not stimulated by bioactive PAF, thus suggesting that PAF may not be directly involved in the stimulation of uterine contractility in sheep in contrast with data reported for other species.

ABSTRACT MUST BE RECEIVED BY CLOSE OF BUSINESS (5:00 PM), FRIDAY, OCT. 8, 1993.

Mail to:

Ms. Laurie Daniels

The American Board of
Ob-Gyn

2915 Vine Street
Dallas, TX 75204

Select the section that should review this abstract (check one)

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Basic Endocrinology

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Infections

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Clinical Endocrinology

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Contraception

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Basic Perinatology

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Epidemiology

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Clinical Perinatology

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Gynecology

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Immunology

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Presentation Preferred:

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Slide Presentation

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Poster Presentation

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Session Preferred:

Code Number/Category

1.60-Uterine/

Contractility

2.43-Parturition

3.49-

/

Prostaglandin

□ Check here if the first author is a research fellow funded by Institution such as NIH, AGOS, ACOG, etc.

Name of sponsoring organization

**IMPORTANT:** Be sure to stay within border. See sample abstracts, typing, and mailing instructions on the reverse side of this form. Use enclosed check list for abstract preparation. The original typed copy of this abstract form (for reproduction by photo-offset in the 1993 Annual Program of the Society for Gynecologic Investigation) must be submitted, together with two photocopies of the abstract form and ten (10) additional double-spaced copies on plain 8 1/2" X 11" paper. For additional copies, include title, but omit name(s) of author(s) and identifying institution(s). All material must reach Laurie Daniels NO LATER THAN THE CLOSE OF BUSINESS (5:00 P.M.), FRIDAY, OCTOBER 8, 1993. Use air mail or express mail from overseas.

Mailing address of first author (Please print or type)

Rafael Garcia-Villar

Laboratory for Pregnancy and
Newborn Research

College of Vet. Med.

Dept. Physiology

Cornell University, Ithaca, NY 14853

Telephone No. (607) 253-3082

Each abstract form submitted MUST BE SIGNED by a member of The Society for Gynecologic Investigation. As a member of the SGI, I assume full responsibility for the quality of this material and its presentation, if selected. I also assume the $30 penalty fee for retyping and/or corrections as charged by the Program Committee. **In addition, this material will not be published, or presented at a national meeting, prior to its presentation at the SGI, if accepted.**

(Member's Name) Peter W. Nathanielsz, MD, PhD, ScD

(Member's Signature)

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(Member's Phone No.) (607) 253-3082