934 Specialia EXPERIENTIA 33/7

The metabolism of the male antifertility agent 1-amino-3-'chloropropan-2-ol in the'rat

A. R Jones, Carole Murcot t* , D. H. Milton and Jenn i fe r F lynn

Biochemistry Department, University o/Sydney, Sydney, N. S. W. 2006 (Australia), 24 December 1976

Summary. The male an t i fe r t i l i ty agent 1-amino-3-chloropropan-2-ol (ACP, I) has been shown to be metabol ized to ~-chlorohvdrin (I I I) and metabo l i t es of e -chlorohydr in . This accounts for t he similar an t i fe r t i l i ty and renal tox ic i ty effects of b o t h compounds .

In m a n y species, low doses of ~-chlorohydr in (3-chloro- propane- l ,2 -d io l , III) p roduce an immedia te and revers- ible phase of infer t i l i ty in the male by an act ion on epi- d idvmal spe rm: , p resumably by glycolyt ic inhibi t ion 2. I t l~as been suggested a t h a t this low-dose ac t ion involves the epoxide metabo l i t e glycidol (2 ,3-epoxypropanol , VII and t h a t exhib i t ion of renal tox ic i ty wi th higher doses of a -chlorohydr in is due to an oxida t ive metabol ic pa th - way 4 to fl-chlorolactic acid (BCLA, IV) and, u l t ima te ly oxalic acid (IX). Al though m a n y s t ruc tu re -ac t iv i ty studies 5-7 have been repor ted wi th compounds re la ted to the a -ch lorohydr in s t ruc ture , only one analogue ( • 1-amino-3-chloro-propanol , (ACP, I) has shown any com- parable an t i fe r t i l i ty effect 8,9. The resolution of ( • into its isomers has shown the ( + ) - i s o m e r to be toxic and inact ive as an an t i fe r t i l i ty agen t and the ( - - ) - i somer to be devoid of tox ic i ty b u t to possess an t i fe r t i l i ty act iv i ty . On a weigh t basis, ( - - ) -ACP is not as ac t ive as ~-chloro- hyd r in :0 a l though both compounds elicit similar effects and do not cause genetic damage n. As these results sug- gest t h a t the me tabo l i sm of ACP could be l inked to t h a t of ~-chlorohydrin, the me tabo l i sm of ( • was in- ves t iga ted to de te rmine w h e t h e r common in te rmed ia tes were responsible for the an t i fe r t i l i ty act ion and the renal tox ic i ty of b o t h compounds . Ch roma tog rams of urine collected over 250 h f rom i .p. admin i s t r a t ion of a6CI-(• (100 mg/kg) to male Wis ta r rats , showed 4 rad ioac t ive areas ident i f ied 14 as C1- (appear ing in urine f rom 40 to 250 h f rom adminis t ra t ion) , BCLA (48-72 h) unchanged ACP (0-72 h) and c~-chloro- hydr in (0-6 h). This indica tes t h a t ACP is degraded to f l -chlorolactaldehyde (II) which, by oxidat ion, is con-

CH2CI

CHOH !

CH2NH 2

I

/ CHO J

II

~H2CI CHOH J CH20H

III

NHR i

, ~H2. 0 - - CH~SCHgCHI~ ~D =- CH" ~ CHOH COOH

CH2NH 2 CH2NHR

~H2CI COOH CHOH ~ i I COOH COOH

IV

~H2, 0 _-- CH /

!

CH20H

VI

The metabolism of ACP and ~-chlorohydrin.

VII

IX

NHR I

CH,SCH2CH

CHOH COOH I CH20H

VllI

ve r t ed to BCLA (IV) and, b y reduct ion, to e -ch lorohydr in (III). A p p r o x i m a t e l y 66% of the r ad ioac t iv i ty is excre ted over 72 h. Of this, 94% is unchanged ( • 2.5% is ~-chlorohydrin and 3% BCLA. The oxida t ion of ( • to the a ldehyde (II) is t h o u g h t to involve monoamine oxidase as p r e t r e a t m e n t of animals w i th the MAO-in- h ib i tor mebanaz ine :7 had no effect on the excre t ion of unchanged ACP bu t de layed the u r ina ry appearance of e -chlorohydr in and BCLA to 24-41 h and 65-72 h re- spect ively. Ex t rac t ion of urine collected over 5 days f rom repea ted dai ly oral admin i s t r a t i on of ( i ) - A C P (100 mg/kg), sub- sequen t process ing and amino-ac id analyses :s , did no t reveal any cys te ine conjugates cor responding to V I I ( R - - C O C H a, R ' - - H or R - - R ' = C O C H 3 ) or V I I I ( R = COCHa). This indica tes t h a t ACP does no t a lkylate cys- teine (glutathione):9 and t h a t the a m o u n t s of e-chloro-

* Pharmacology Department, Manchester University, Manchester M13 9PL / England.

1 E.R. A: Cooper, A. R. Jones and H. Jackson, J. Repro& Fertil. 38, 379 (1974).

2 H. Mohri, D. A. I. Surer, P. D. C. Brown-Woodman, I. G. White and D. D. Ridley, Nature Loud. 255, 75 (1975).

3 H. Jackson, I. S. C. Campbell and A. R. Jones, Nature Loud. 226, 86 (1970).

4 A.R. Jones and C. Murcott, Experientia 32, 1135 (1976). 5 R.J . Ericsson and G. A. Youngdale, J. Reprod. Fertil. 21, 263

(1970). 6 J .D. Hahn, Nature Lond. 226, 87 (1970). 7 U.K. Banik, T. Tanikella and S. Rakhit, J. Reprod. Fertil. 30,

117 (1972). 8 R. Paul, R. P. Williams and E. Cohen, Contraception 9, 451

(1974). 9 J .A. Coppola and R. J. Saldarini, Contraception 9, 459 (1974). 10 H. Jackson and 13. Robinson, Chem. biol. Interae. 13, 193 (1976), 11 P. Jones and H. Jackson, Contraception 73, 639 (1976). 12 Hydrolysis of 1-(N-phthalinfido)-2,3-epoxypropane 13 in Ha*C1

gave a6C1-ACP as the Ha6C1 salt. Dat a presented here have been corrected for the excretion of HasC1.

13 S. Gabriel and H. Ohle, Chem. Ber. 50, 819 (1917). 14 Chloride ion was identified by the method of Seiler and Kaffen-

berger 15, BCLA and ~-chlorohydrin according to Jones 16 and ACP by means of a Jeol amino acid analyzer.

15 H. Seiler and T. Kaffenberger, Helv. chim. Aeta dd, 1282 (1961). 16 A. R. Jones, Xenobiotiea 5, 155 (1975). 17 Mebanazine oxalate was kindly supplied by ICI Pharmaceuticals,

Macelesfield, Cheshire. 18 Urine was ehronlatographed on Whatmans 3MM paper ill n-

butanol: acetic acid: water (4 : 2 : 1) and areas corresponding to authentic VII (R~COCH 3 R=H, R=R'=COCHa and R = R ' = H ) and V I I I (R=H and R=COCHs) eluted with water. Where acetylated derivatives were suspected, acid hydro- lysis (5NHCI, 90~ 1 h) was performed. All extracts were purified on Dowex-50W columns and examined on a Jeol amino acid analyzer against authentic VII (R=R '=H) and V I I I (R--H). The sensitivity of this procedure was such that it was capable of detecting less than a 0.5% conversion of I to VI I and VIII .

19 A. R. Jones, Drug Metab. Rev. 2, 71 (1973).

15.7. 1977 Speeialia 935

hydr in p roduced are insuff ic ient to form V I I I ( R = H ) , since th is conjugate is no t de tec tab le af ter admin i s t r a t ion of the low-dose regime of e -ch lorohydr in which causes infert i l i ty. A t t e m p t s to de tec t the a ldehyde (II) as a u r inary me- tabol i te have been unsuccessful t hough in ra t l iver ho- mogenates , the convers ion of e -ch lorohydr in to BCLA ( I I I - -~ IV) has been d e m o n s t r a t e d to involve N A D +- l inked dehydrogenase ac t iv i ty wi th the fo rmat ion of an as ye t un ident i f ied a ldehyde: Ra t s given 36Cl-e-chloro- hydr in af ter p r e t r e a t m e n t wi th d isu l furam to inh ib i t a ldehyde dehydrogenase 2~ show a delay in the onse t of excre t ion of BCLA (IV) in the urine (from 5 h to 9 h) and t race amoun t s of an ~-halohydr in a ldehyde can be de tec ted f rom 5 to 9 h af ter adminis t ra t ion .

I t is t e m p t i n g to pos tu la te differing enzyme specificities for the ( + ) - and ( - - ) - i somers of the a ldehyde (II) by the dehydrogenases I I - + IV and I I - ~ I I I . This would ex- pla in preferent ia l BCLA and oxalic acid fo rmat ion by ( + ) - A C P , leading to renal toxic i ty , and e -ch lorohydr in p roduc t ion by ( - - ) -ACP yielding an an t i fe r t i l i ty response since oxalic acid is de tec tab le 22 only as a u r inary me tab - olite of ( + ) - A C P and no t f rom ( --)-ACP. The compara t ive me tabo l i sm of ( + ) - and ( - - ) -A CP in vivo and in vi t ro is a t p resen t under inves t igat ion.

20 N.O. Kjeldgaard, Acta pharmac, tox. 5, 397 (!949). 21 J. Hald and V. Larsen, Acta pharmac, tox. 5, 292 (1949). 22 C. Murcott, M. sc. Thesis, Manchester 1976.

C o m p a r i s o n of b i cyc l i c p h o s p h o r o u s e s t e r s w i t h b icucu l l ine and p i c r o t o x i n as a n t a g o n i s t s of p r e s y n a p t i c inh ib i t ion in the rat cuneate nuc l eus

N. Davidson, E d n a I. Macfar lane and Diane L. Michie 1

Department o/ Physiology, Marischal College, University o/Aberdeen, Broad Street, Aberdeen A B 9 1A S (S~otland), 22 December 1976

Summary . The effects of 2 of a series of bicyclic phosphorous esters, the e thy l (EPTBO) and isopropyl (IPTBO) com- pounds , were compared wi th those of the GABA antagonis ts , p ic ro toxin and bicuculline, on p resynap t i c inhibi t ion in the ra t cunea te nucleus. B o t h E P T B O and I P T B O were found to be effective, reversible an tagonis t s of p re synap t i c inhibi t ion, wi th I P T B O a p p r o x i m a t e l y 10 t imes more p o t e n t t h a n E P T B O and equ ipo t en t wi th bicuculiine, E P T B O equ ipo t en t wi th p icrotoxin .

The 7 -aminobutyr ic acid (GABA) antagonis ts , bicucull ine and picrotoxin, have been repor ted to be effective an tago- nists of p resynap t i c inhibi t ion in the ve r t eb ra t e spinal cord and dorsal co lumn nuclei ~-6. In addi t ion b o t h p ic ro toxin and bicucull ine block the di rect depolar iz ing act ions of GABA on p r i m a r y af ferent te rminals s-8 sug, gest ing t h a t the blocking of p resynap t i c inhibi t ion by

100

O -

g n < v 0 20 40 60 80 100 120 140 160 min

EPTBO 10-3M Time

Depression and recovery of the cuneate P wave during application and after removal of 10 -3 M EPTBO. Tile sample recordings of the computer-averaged cuneate evoked potential shown above the graph are taken from left to right, before application of EPTBO, during maximum depression of the P wave in the presence of EPTBO and ahnost 2 h after its removal, as indicated. Each computer record is an average of 16 successive recordings of the supramaximal response to ipsilateral forepaw stimulation; sweep time is 100 msec. The first negative, upward going component of the response (the N wave) is unaffected by EPTBO, while the second, positive going component (the P wave) is virtually completely abolished. The graph below the computer records shows the time course of depression and recovery expressed in terms of the area of P wave as a percentage of its mean control size.

these subs tances is due to a discrete act ion a t GABA- nergic receptors on p r i m a r y af ferent terminals . I t is in te res t ing therefore to examine the effect on p resynap t i c inhib i t ion of a new group of subs tances , the bicyclic phos- phorous esters, which have recent ly been repor ted to be effect ive GABA an tagon i s t s in the ra t super ior cervical ganglion 9. Materials and methods. Adul t ra t s were anaes the t i sed wi th a 1% chloralose-10~ ure thane solut ion (0.8 ml/100 g i .p.) and the pial surface of the dorsal co lumn nuclei exposed for electrical recording and drug appl icat ion as descr ibed elsewhere 6. Evoked po ten t ia l s were recorded f rom tile pial surface of the cunea te nucleus following sup ramax ima l electrical s t imula t ion of the ipsi lateral fo repaw wi th a 0.1 msec s t imulus del ivered th rough p.c. needle electrodes. Groups of 16 successive evoked po ten- t ials were compu te r - ave raged dur ing superfus ion of the pial surface wi th an artificial cerebrospinal fluid (csf) solut ion 1~ or wi th similar solutions conta in ing 10 .3 or

1 The authors are grateful to Dr J. F. Collins, Deparunent of Chemistry, Sir John Cass School of Science and Technology, 31 Jewry Street London, for the gift of bicyclic phosphorous esters.

2 J .C. Eceles, R. F. Schmidt and W. D. Willis. J. Physiol. 168, 500 (1963).

3 R.F. Schmidt, Pflfigers Arch. 277. 325 (1963J. 4 N. Davidson and E. E. Suckling, Fedn Proc. 26, 491 (19671. 5 N. Davidson and H. Reisine. Nature New Biol. 234, 223 (1971). 6 N. Davidson and C A. P. Southwick. J. Physiol. 219, 689 (19711. 7 R.A. Levy and E. G. Anderson, Brain Res. 43. 171 11972/. 8 R.A. Davidoff, Exp] Neurol. 35. 179 /19721. 9 N.G. Bowery, J. F. Collins and R. G. Hill; Nature 261 601

(1976). 10 J. K. Merlis, Am. J. Physiol. 137, 67 (19401.