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Effects of Methylthiouracil onProlactin Levels and Tail Heightin Triturus Cristatus CarnifexGiovanni Lodi a , Camillo Vellano a & Valdo Mazzi aa Istituto di Anatomia comparata , Università diTorinoPublished online: 14 Sep 2009.

To cite this article: Giovanni Lodi , Camillo Vellano & Valdo Mazzi (1974) Effects ofMethylthiouracil on Prolactin Levels and Tail Height in Triturus Cristatus Carnifex ,Bolletino di zoologia, 41:1, 59-62, DOI: 10.1080/11250007409430088

To link to this article: http://dx.doi.org/10.1080/11250007409430088

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Boll. Zoll. 41 : 59-62, 1974

'EFFECTS OF METHYLTHIOURACIL ON PROLACTIN LEVELS .AND TAIL HEIGHT I N TRITURUS CRISTATUS CARNIFEX

L'ipofisi di femrnine di Tritone crestato allevnte per 120 giorni in una soluzione -a1 2%,, di metiltiouracilc, coltivate in vifro per tre ore, rilasciano ncl brodo di coltura quantitj. significativnmentc minori di prolattina rispetto alle ipofisi di animali di con- trollo. Kegli animali trattnti con il tioureico l'altezza della pinna caudalc, un carattere ambiscssuale prolattina dipendente, i: rimasta significativamente minore rispetto ai controlli per tutta la durata dell'csperienza. Questi dati indimno die nel Tritonc crcstato il tiourcico escrcita un cffctto inibitore sulla increzione, e probabilmente nnche sulla .sintcsi di prolattina.

It lias long been known that prolactin secretion is stimulated by thyroidal hormones (NICOLL and MEITES, 1903), while being inhibited by hypothyroidism (MEITES and TURNER, 1047). In tlic rat the thyroidal .hormones and thiourcics act directly and in the opposite sense on the anterior pituitary. Both treatments are in fact operative on pituitaries .cultured in vitro, while in vivo they modify in no may the content of the hypothalamic prolactin inhibiting factor (PIF) (CIIEN and ~IEITES, 19G9).

Recently, however, DOERR SCIIOTT and coworkers (1972) were ablc to establish, by means of electron microscopic studies of the pituitary from the rat, that propylthiouracil (PTU) administration leads to thc activation not only of the tliyrotropie cells, as expected, but of the pro- lnetin producing cells as well. Since recent observations have provided conflicting evidence that the hypothalamic thyreotropic releasing hormone (TRH) administered in vivo enhances prolactin release in man, some labo- ratory mammals and bovines (for the bibliography see GUAL et al., 1972 ; Lu et al., 1972 ; SCIKALLY et al., 1973 ; Coxmy et al., 1973), DOERR Scnom and coworkers believe that their submicroscopic findings may be inter- preted in terms of n rise in TRH production as a consequence of the drop in thyroidal hormone blood !level brought about by PTU.

The present investigations were undertaken in an attempt to verify in a urodele amphibian which of the two opposed evaluations of the effects exerted by thioureics, proposed by CrrEN and ~IEITES and respectively by DOERR SCIIOTT et al., be valid.

Experimkiitol procedicre - 10 crested newt adult females, supplied by commercial dealers, were raised in glass containers in two liter of water from 27/6/1973 t o 26/10/1973 at room temperaure. Water was changed every other day. Ten females mere raised for the same lapse of time in a 0.2% methylthiouracil (MTU) (IIerck) solution under the same con-

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ditions. Two controls and five thiouracil-treated specimens died during treatment.

Tail height - The height of the caudal fin mas measured in all tlie animals a t tlie start of the treatment, after 80 days and a t autopsy, by means of a micrometer caliper supplied with a precision screw with gra- duation that can be read in tcntlis of a millimctcr.

In uitro ctclture and pigeon crop test - The pituitary of each animal was escised under BIS 222 anesthesia under aseptical conditions, then cultivated in 1 ml of Difco medium 100 for 3 hr. Thereafter each hypophysis was homogenized in 0.5 ml of 0.9% NaC1; the culture medium was dialyzed against distilled water for 12 h at 4oC then liophylized and rediluted in 0.8 ml of 0.9% NnCI. The homogenate of each pituitary and the liophilyzed from the relative culture medium were used for the pigeon crop test ac- cording to the technique already reported elsewhere (VELLAKO et al., 1068). The activity curvc was obtained by using respectively 50, 100 and 200 i.m.u. of NIH ovine prolactin P-S 10 (mean activity 25.6 I.U./mg).

The results obtained by the pigeon crop test and those concerning the percent tail development are shown in tables 1 and 2 respectively. From inspection of table 1 it can be sccn that the pituitary prolactin levcl does not differ significantly between treated animals and control animals, whereas the hormone amount released in tlie culture medium is signifi- cantly higher (P 0.001) in control animals than in the thioracil-treated ones.

Table 2 slioms that in the treated animals tail height (a prolactin dependent ambisesual character: see VELLASO et al., 1070; Mazzz et al., 1071) has remained consistently lower than in controls, whereby the conclusion can be drawn that the release, possibly the synthesis as mcll, of prolactin has been interfered with by 3ITU administration throughout treatment. This inhibition has also been operative during the critic period (temperature decline in autumn) in which prolactin, after being stored in typc I acidopliils during summcr, is released in nature (cf. 1\lAzzr, 1070).

The present results arc therefore in keeping with those reported by CIIEN and JIEITES (10GI)), although they do not permit to establish mhether tliiouracil acts directly on tlie hypophysis, as it does in tlie rat, or through rcinforccmcnt of hypothalamic PIP production, or conversely, by inhi- biting PRF (prolactin releasing factor), which has been postulated to be present also in the crested newt (VELLAXO ct al., 1068).

Acknorcledgtnents. Prolactin was obtained through thc gcncrosity of Dr. A. E. WUILELXI, Endocrinology Study Section, National Institutes of Health.

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REFERENCES

CHES C. L. and MEITES J., 1969 - Proc. SOC. Exptl. 13Iol. Med., 131 : 570-578. COXVEY E. N., TUCKER H. A., SMITH V. G. and ZOLXAN J., 1973 - Endocrinology, 92 :

DOERR-SCROTT J., STOECKEL AI. E., PORT A. and REVILLE P., 1972 - C.R. Amd. Sc,

GUAL C., KASTIN A. J. and SCEALLY A. V., 1972 - Rec. Frogr. Hormone Res., 48 : 173-200- L u I<. H., SIXAAR J., KORTRIQIIT I<. H. and MEITES J., 1972 - Endocrinology, 81 :

XAZZI V., 1970 - In : ~ \ ~ R T I N I L., ~ ~ O T T A 31. and FRASCEINI I?. (Eds.) : The hypofhola-

YAZZI V., VELLANO C. and COLUCCI D., 1971-72 - Atti Accad. Sci. Torino, 1 C1. Sci. Mat,

MEITES J. and TURNER C. W., 1947 - Proc. SOC. Exptl. Biol. Med., 6% : 455. NICOLL C. S. and MEITES J., 1963 - Endocrinology, 72: 544-551. SCHALLY A. V., ARINURA A. and I ~ S T I N A. J., 1973 - Science, 1 i S : 341450. VELLANO c., MAzzI V. and SACERDOTE N., 1970 - Gem comp. Endocrinol., 14 : 535-541.. VELLAXO C., PEYROT A., LODI G., LONGO S. and MAzzI V., 1068 -Boll. Zool., 36 : 177-188-

471-470.

Paris, 174 : 2996-2997.

15.tO-1545.

tnus, Academic Press, New Yorli and London, pp. 063-676.

Fis. Natur., 106: 129-135.

December 28, 1973 GIOVANNI LODI CANILL0 VELLANO VALDO MAZZI Istituto di Anatomia comparats Universith di Torino

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