Gidley-Baird, A A

Hau, J

White, Barbara M

English

Journals from University of Tartu

Scuml. _I. 11111). Anim. Sci. 12;. firg’. nr. 1. 1980Increased ovulation rate in Virgin mice induced by malesby A. A. Gidley-Bairdl), Barbara M. VV/‘IiteU & ]. Han?)1) Department of Veterinary Physiology, University of Sydney, N.S.W., Australia.2) Institute of Pathology, Laboratory Animai Unit, RoyaI Veterinary and AgriculturalUniversity, Copenhagen, Denmark.IntroductionThe pheromonal regulation of the ovariancycle in many species including mice hasrecently been extensively reviewed (Van-denbergh 1983).It is generally known that if a male miceis introduced into a cage with female mice,which have previously lived in a group offemales thereby syncronizing their oestruscycles, the majority of the females will bein oestrus three days later (Whitten 1958).The male has a luteolytic effect which re—lases the gonadotrophin surges and even—tually results in oestrus and ovulation(Bronson 1975, Ryan & Schwartz 1977).Male induced oestrus is similar to spon-taneous oestrus With regard to reproductiveorgan weights and pituitary luteinizinghormone content (Bingel &Schwartz 1969).The present study was undertaken in orderto determine whether contact with malesaffected the number of ova shed by femalemice at oestrus, and if the number variedas a function of the time spent with themales prior to ovu1ation.Table 1.Materials and methodsVirgin female mice of the outbredQuackenbush (QS) stock aged 8—10 weeks,weighing 25—30 gm and raised in isolationfrom males were used in all experiments.The female mice were allocated two percage among either a colony of intact malemice or a colony of vasectomized males.The mice were maintained in rooms withcontrolled temperature (230—27OC) andhumidity (55 0/0—60 0/0). Artificial lightingwas provided by fluorescent tubes whichwere switched on and off automatically at06.00 h and 18.00 h respectively.The female mice were killed 24 hours afterthe detection of a copulatory plug, theoviducts were removed and flushed with0.9 0/0 NaCl solution and the number ofova recovered from each oviduct wererecorded.This experiment was repeated four timesto obtain a minimum of 60 mice matedwith intact males and 60 mated with vas-ectomized males on each of days 1—4 aftersetting up with the males.Number of ova recorded in females (group size 30) which matedon days 1, 2, 3 or 4 after housing with intact or vasectomized males. Day of matingafter placingwith malesDay 1 Day 2 Day 3 Day 4No. of ova ii SE. matedwith intact C?‘13.2 :L- 0.42 No. of ova ii S.E. matedwith 13.4 i 0.38vasectomized d‘14.3 i 0.4414.7 i 0.3915.4 i 0.35 14.9 i 0.49Results and discussionThere was a significant increase in thenumber of eggs found in females whichmated on days 2, 3 0r 4 after housing withintact or vasectomized males. when matedon day 1 (p < 0.05, p < 0.01 and p < 0.01respectively) (Table 1).This experiment was repeated using fema—les which were housed 20 per cage andplaced in the same room as the males forthree days prior to distributing the fema1esamong the males. The result did not differfrom those found in the previous experi—ment.To evaluate whether the increased ovula—tory response was mediated via male in—duced increase in pituitary release offollicle stimulating hormone (FSH), fe-males were injected immediate1y prior tocontact with the males with either 0.1 m1of normal rabbit serum (NRS) or 0.1 m1of an anti rat FSH (ARFSH) raised in arabbit.Immunological cross-reaction between ratFSH and mouse FSH was indicated sincea crude mouse pituitary extract gave posi—tive reaction in a double antibody radio-immunoassay employing the ARFSH.In accordance with the results of theprevious experiments a significantly largernumber of eggs (p < 0.02) were 0vu1atedon day 3 compared with day 1 after in—troduction 0f the males in the group offemales treated with NHS (Table 2). ByTable 2. Number of ova recorded in femaleswhich were injected immediateiy prior to con—tact with normal male mice with either 0.1 m1of normal rabbit serum (NRS) or 01 ml of arabbit anti rat FSH serum (ARFSH) (Groupsize 50). Day of mating afterplacing with intact 6‘ Day 1 Day 3N0. 01 ova i i SE.0.1 ml NRS 13.3 i 0.51 14.9 i— 0.4N0. of ova i : 8.13.0.1 m1 AR FSH 12.8 i 056 13.3 i— 0.5 Scand. _]. Lab. Anim. Sci. 13. zirg. nr. 1. 1986contrast, no significant increase from day1 to day 3 was found in the group of fe~males which prior to the male contact hadbeen treated with ARFSH.This experiment suggests that FSH maybe an important factor in the effect ofmales 0n the number of ova shed by fe—males, and consequently it was tried outwhether it was possible to enhance theeffect of the males by administering FSHto the females.The female mice were injected with either10 gig or 50 11g of rat FSH (NIH B—l) in0.1 m1 of gelatine vehicle or vehicle alonejust prior to their housing with males.Table 3 shows the comparison betweennumber of ovulated eggs in the FSH treat—ed groups and the control group whichmated an day 1 or day 3 following contactwith the males.Table 3. Number of ova recorded in femaleswhich were injected with 10 lug or 50 pg ratFSH in 0.1 m1 of a 15 0/0 gelatine vehicle orvehicle alone just prior to housing with nor-ma1 male mice (Group size 30). Day after placing with intact 07‘ Day] Day?»N0. of ova i i 8.13.0.1 ml 15 0/0 gel 12.6 i 0.62 14.8 "t_- 0.41No. of ova i t SE.10 pg rat FSH 13.0 i 0.52 17.6 i 0.87No. of ova i i 8.13.50 0g rat FSH 13.1 i 0.6 25.1 i 2.41There was no significant difference innumber of eggs between animals in thethree groups which mated on day 1. but asignificant difference was seen in all threegroups when comparing number of eggs inthe animals mating on day 1 comparedwith those mating on day 3.The administration of 10 and 50 gig FSHhad a significant positive effect on thenumber of eggs ovulated on day 3 (p <0.001).19The conclusion drawn from this work isthat virgin mice ovulate a significantlygreater number of eggs it they are in con-tact with males for a period of time priorto ovulation, and that this response ap—pears to involve an increased release ofFSH.These findings have important implica-tions, because they indicate that there is alinear relationship between the number ofeggs ovulated by female mice and thelength of time spent with the males priorto mating. This suggests that, when usingeither number of eggs ovulated 0r littersize as a measure of an effect of any ex-perimental treatment one should be cau—tions not to mix females mated on differ—ent days after the intraduction 0f the ma-les. All experiments should be standardiz—ed. comparing only females mated aftersimilar periods of time spent with themales prior to mating7 in order to avoidthe variation in number of eggs ovulatedto influence the experimental results.ReferencesBingel, A. S. & N. B. Schwartz (1969): Tim-ing of LH release and ovulation in thecyclic mouse. I. Reprod. Fert. 19, 223—229.Bronson, F. H. (1975): Male induced pre-cocial puberty in female mice: confirma—tion of the role of estrogen. Endocrinology.96, 511—514.Scand. J. Lab. Anim. Sci. 13. irg. nr. 1. 1980Ryan, K. K. & N. B. Schwartz (1977): Groupedfemale mice: demonstration of pseudopreg—nancy. Biol. Reprod. 17, 578.Vandenbergh, .l' G. (ed) (1983): Pheromonesand Reproduction in Mammals. AcademicPress.lz’l/hitm, W. K. (1958): Modification of theoestrus cycle of the mouse by externalstimuli associated with the male. Changesin the oestrus cycle determined by vaginalsmears. J. Endocr. 17, 307.SammendmgDet er velkendt, at nar en hanmus anbringesi et bur med hunmus med estrussynkroni,kommer starstedelen af hunnerne i estrus tredage senere.Denne undersegelse Viser, at hunmus, der par—res pa dag 3, efter hannen er blevet introdu—ceret, ovulerer signifikant flerc Beg end dehunner, der parres dag 1 0g dag 2.Dette respons syntes at involvere en eget ud—skillelse at follikel stimulerende hormon(FSH).Resultaterne indicerer, at eksperimenter meddraegtige mus bar standardiseres, siledes at kunhunner, parret efter samme antal dage tilbragtmed hannen, sammenlignes. I modsat fald kanden systematiske forskel i antallet af ovuleredeaeg afhaengig af parringsdag fare til forkerttolkning at forsagsresultatcr.To whom correspondence and requests for reprints should be addressed:Dr. J. Han, Institute of Pathology, Laboratory Animal Unit,Royal Veterinary and Agricultural University, 13 Biilowsvej, 1870 Frederiksberg C,Denmark. SCAND LAS MEMBERSHIP &ANNUAL SUBSCRIPTION 120 Skr21

Increased ovulation rate in virgin mice induced by males

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Increased ovulation rate in virgin mice induced by males

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