Animal Reproduction Science, 15 (1987) 259-263 259 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

Genital Tract Deve lopment and His tomorphometr ica l Traits of the Testis in the Young Boar: Relat ionships with Fat Androstenone Levels

M. BONNEAU', J. CARRIE-LEMOINE' and MESURE-MORAT 2

' I.N.R.A., Station de Recherches Porcines, Saint Gilles, 35590 l'Hermitage (France) 2Universitd de Clermont Ferrand, Equipe de Cytophysiologie, Laboratoire de Biologie Cellulaire et Gdndtique, B.P. 45, 63170 Aubiere (France)

(Accepted 28 August 1987)

ABSTRACT

Bonneau, M., Carri~-Lemoine, J. and Mesure-Morat, M., 1987. Genital tract development and histomorphometrical traits of the testis in the young boar: relationships with fat 5ol-androsten- one levels. Anim. Reprod. Sci., 15: 259-263.

Genital tract development and histomorphometrical traits of the testis were measured at slaughter, at 180 days of age, in a total of 12 boars in which fat 5~-androstenone levels had been previously determined at 100, 125, 150 and 175 days of age. In seven animals a peri-pubertal rise in fat 5~-androstenone level was observed ("high androstenone", HA boars) whereas it was not in the other five pigs ("low androstenone", LA boars). There was no significant difference be- tween HA and LA boars for testis, epididymis, seminal gland or bulbo-urethral gland weights. LA boars had significantly fewer and smaller Leydig cells than HA pigs.

From the present and previous results it is concluded that fat 5a-androstenone level is not solely dependent on sexual maturation. There is a large between-boars variability in the potential for 5o~-androstenone production, which is probably under genetic control.

INTRODUCTION

5c~-andros tenone (5c~-androst - 16 -en -3 -one ) , one i m p o r t a n t c o m p o u n d re- spons ib le for b o a r ta in t , is s y n t h e s i z e d in t he b o a r tes t i s a long wi th o the r 16- a n d r o s t e n e s teroids , a n d r o g e n s a n d e s t rogens (Gower , 1972) . At p u b e r t y fa t 5 ~ - a n d r o s t e r o n e level r ises s ha rp l y ( Claus, 1975 ). However , the a m p l i t u d e of th i s 5 ~ - a n d r o s t e n o n e inc rease is ve ry va r i ab le b e t w e e n a n i m a l s ( A n d r e s e n , 1976) a n d some ind iv idua ls do no t even exh ib i t a n y s ign i f ican t r ise ( B o n n e a u and Desmoul in , 1980). T h e lack of a n d r o s t e n o n e increase in some boars a round p u b e r t y c a n n o t be r e l a t ed to a n y s ign i f ican t a l t e r a t i o n in p l a s m a L H a n d tes- t o s t e r o n e prof i les ( B o n n e a u et al., 1987) .

0378-4320/87/$03.50 © 1987 Elsevier Science Publishers B.V.

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The present study was undertaken in order to determine the relationships between the patterns of fat 5a-androstenone variation with age and genital tract development or histomorphometrical traits of the testis. The results about age-related changes in plasma LH and testosterone concentration profiles and fat 5a-androstenone levels are reported in another paper (Bonneau et al., 1987).

MATERIAL AND METHODS

Animals

Twelve young boars of the Large White breed were involved in the experi- ment. Fat 5a-androstenone levels were measured at 100, ,125,150 and 175 days of age (Bonneau et al., 1987 ). At 180 days of age, the animals were slaughtered, the genital tracts collected and immediately dissected. Testis, epididymis, sem- inal gland and bulbo-urethral gland weights were recorded. Samples of testis tissue were taken for histomorphometric studies.

Histomorphometric study of the testis

Histomorphometric study of the testis and estimation of Leydig cell number were performed on fixed tissue fragments embedded in paraffin. Sections 7 pm in thickness were stained with Heidenhain's azan. The diameters of seminif- erous tubules, Leydig cells and Leydig cell nuclei were measured on photo- graphs taken at random. For Leydig cell counting, the Floderus-Abercrombie technique (Abercrombie, 1946) was used, which takes into account nuclear size and section thickness. Number of Leydig cells per g testis and total number of Leydig cells in both testes were calculated.

Statistical analysis

Differences between groups were assessed by analysis of variance. Correla- tions between fat 5a-androsterone levels, genital tract development and his- tomorphometrical traits of the testis were calculated, using the Spearman rank coefficient of correlation ( Siegel, 1956).

RESULTS AND DISCUSSION

Age-related changes in fat 5a-androstenone levels were previously reported (Bonneau et al., 1987 ). Seven boars exhibiting high 5a-androsterone levels at 150 and 175 days of age were allocated to group "high 5c~-androstenone" (HA). The remaining 5 animals were allocated to group "low 5a-androstenone" (LA).

There was no significant difference between HA and LA animals for testis,

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TABLE 1

Genital tract development and histomorphometrical traits of the testis ("high 5a-androstenone" HA vs "low 5o~-androstenone" LA boars; means _+ s.e.m.)

HA LA Difference boars boars

Weight of Testes (g) 468 _+ 67 563 ___ 38 NS Epididymis (g) 109 _+ 11 104 _+ 6 NS Seminal vesicles (g) 263 _+ 46 277 _ 33 NS Bulbo-urethral glands (g) 240 _ 19 186 _+ 13 NS

Diameter of Seminiferous tubules (/an) 207_+ 7 193 + 8 NS Leydig cells (/~m) 191 _ 3 156___ 6 P < 0.01 Leydigcell nuclei (/~m) 74___ 1 66___ 2 P < 0 . 0 5

Number of Leydig cells Total (109) 84 _ 10 46 ___ 10 P < 0.05 per g testis (106) 135 _+ 18 83 _ 19 NS

epididymis, seminal gland and bulbo-urethral gland weight or seminiferous tubules diameter (Table 1 ).

HA animals had more total Leydig cells (84 vs 46 × 109, P < 0.05; Table 1 ) and Leydig cells per g testis (135 vs 83× 106, NS) than LA boars. The total number of Leydig cells was significantly related to the number of Leydig cells per g testis (Rs = + 0.98, P < 0.001 ) but not to the weight of testes (Rs = + 0.36, NS). Therefore, the observed difference in Leydig cell number between HA and LA animals was not due to a difference in testis weight. It was rather the result of a higher number of Leydig cells per g testis.

Leydig cell and Leydig cell nucleus diameters were higher in HA than in LA boars (cell diameter 191 vs 156/~m, P<0.01; cell nucleus diameter 74 vs 66 /~m, P < 0.05; Table 1 ). In agreement with previous observations by Groth and Claus (1977), fat 5a-androstenone levels at 125, 150 and 175 days of age were positively related to the diameter of Leydig cells ( R s = 40.71, P<0 .05 to R s = + 0 . 8 8 , P<0.01; Table 2) and the diameter of Leydig cell nuclei ( R s = + 0.73, P < 0.05 to R s = + 0.83, P < 0.01 ). Bulbo-urethral gland weight was also positively related to the number of Leydig cells ( R s = + 0.64 to + 0.74, P < 0.05 ) and the diameter of Leydig cell nuclei (Rs = + 0.65, P < 0.05 ). Since bulbo-urethral glands are target organs for androgens and estrogens (Joshi and Raeside, 1973; Morat et al., 1980; Booth, 1980, 1983; Lauwers et al., 1981 ), such relationships are consistent with the results of Lunstra et al. (1986) who reported significant correlations between Leydig cell or Leydig cell nucleus

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TABLE 2

Relationships between histomorphometrical traits of the testis, genital tract development and fat androstenone levels {Spearman rank coefficients of correlation)

Diameter Number of Leydig cells

Seminiferous Leydig Leydig Total /g testis tubules cells cell nuclei

Weight of Testes 0.77* 0.07 0.35 0.36 0.19 Epididymis 0.81" 0.38 0.62 0.14 0.05 Seminal vesicles 0.41 0.09 0.14 0.20 0.20 Bulbo-urethral glands 0.43 0.52 0.65* 0.74* 0.64*

Fat androstenone levels 100 days 0.30 0.23 0.16 -0.17 -0.12 125 days 0.25 0.71" 0.73* 0.43 0.40 150 days 0.06 0.88** 0.83** 0.57 0.60 175 days 0.07 0.83** 0.75* 0.71" 0.74*

*P<O.05; **P<O.Ol.

volume and the Leydig cell in vitro testosterone and estradiol producing capacity.

There was no indication of impaired sperm production in LA boars as com- pared with HA animals since active spermatogenesis was observed and nu- merous spermatozoa were present in seminiferous tubules of all animals.

CONCLUSION

A peri-pubertal rise in fat 5a-andros tenone level was observed in some pigs (HA boars ) whereas it was not in other animals (LA boars ). The lack of 5~- androstenone increase in LA pigs is probably not the result of delayed sexual maturat ion since there was no significant difference between HA and LA boars in LH and testosterone secretory profiles (Bonneau et al., 1987) or genital tract development. The reduced size and number of Leydig cells in LA animals suggest that such animals would exhibit reduced capacity for overall steroid production. However, testosterone levels as well as accessory sex gland weights were similar in HA and LA boars. Therefore, it seems more likely that LA animals exhibit reduced capacity for production of 16-androstenes. The litter effect on fat 5t~-androstenone pat terns (Bonneau et al., 1987) suggests that the capacity for 16-androstene production is under genetic control: inability to synthesize high amounts of 5c~-androstenone would be the result of impaired activity of the specific enzyme system (andien-fl synthetase; Gower, 1972) initiating the 16-androstene biosynthetic pathway. In good agreement with

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that hypothesis, Sellier and Bonneau (1987) selected a line of boars exhibiting both reduced fat 5a-androstenone content and unaffected genital tract devel- opment, as compared to control animals.

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