Effects of (R)-deoxycoformycin (pentostatin) on intrauterine nucleoside catabolism and embryo viability in the pregnant mouse.
The viability of early mouse embryos is acutely sensitive to (R)-deoxycoformycin (pentostatin), a tight-binding inhibitor of adenosine deaminase (ADA). Previous studies have shown that a single 5-mg/kg dose on day 7 (plug = day 0) of gestation fully inhibits uteroplacental ADA activity within 0.5 h; causes massive cell death in the neural plate and primary mesenchyme by 6 h, major craniofacial anomalies by day 10, and resorption by day 12 (Knudsen et al., '89; Airhart et al., '91). The present study has examined further the developmental toxicity and early effects of this inhibitor on ADA metabolism. (R)-Deoxycoformycin was administered to pregnant CD-1 (ICR) mice as a single intraperitoneal dose of 0.5-10 mg/kg total body weight on days 6-11 of gestation. The major adverse effect, early resorption, was dose dependent and specific to day 7-8 exposure. Treatment with 5 mg/kg on day 7 resulted in 85% resorptions, 15% malformations, and a 24% reduction in mean fetal weight, whereas the same dose of (S)-deoxycoformycin had no effect. Levels of adenosine and 2'-deoxyadenosine, which are the endogenous substrates of ADA, were monitored in the embryo/decidual unit (E/D) by reversed-phase high-performance liquid chromatography (RP-HPLC). In response to the inhibitor, both nucleosides increased transiently in the antimesometrial compartment (antimesometrial decidua + embryo). Peak levels (Cmax) of adenosine and 2'-deoxyadenosine were dose dependent over the range tested (0.05-10 mg/kg). Exposure to 5 mg/kg on day 7 raised adenosine levels within 0.5 h to 42-fold over the basal level of 0.06 nmol/mg protein. There was an even stronger effect on 2'-deoxyadenosine levels, which were elevated 674-fold over the detection limit of 0.0005 nmol/mg protein. Direct exposure to the inhibitor in serum-free E/D culture produced similar results: 50 microM (R)-deoxycoformycin within 1 h raised adenosine levels 26-fold and 2'-deoxyadenosine levels 410-fold. In vivo studies also showed a general correlation between embryolethality and the length of adenine nucleoside pool expansion, apparent for exposure on day 7, 8, or 9 but not on day 6, suggesting that the embryo becomes sensitive to adenosine or 2'-deoxyadenosine once the neural plate has formed.
Knudsen
T B
TB
Department of Anatomy, Jefferson Medical College, Philadelphia, Pennsylvania 19107.
Winters
R S
RS
Otey
S K
SK
Blackburn
M R
MR
Airhart
M J
MJ
Church
J K
JK
Skalko
R G
RG
D000241:Adenosine / Q000378:metabolism*; D000243:Adenosine Deaminase / Q000378:metabolism; D058892:Adenosine Deaminase Inhibitors; D000818:Animals; D046508:Culture Techniques; D003839:Deoxyadenosines / Q000378:metabolism*; D005314:Embryonic and Fetal Development / Q000187:drug effects; D005260:Female; D005313:Fetal Death / Q000139:chemically induced; D005327:Fetal Resorption / Q000139:chemically induced; D005328:Fetal Viability / Q000187:drug effects*; D006706:Homeostasis; D007288:Inosine / Q000378:metabolism; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D015649:Pentostatin / Q000737:chemistry / Q000633:toxicity*; D011247:Pregnancy; D011684:Purine Nucleosides / Q000378:metabolism; D013237:Stereoisomerism; D013723:Teratogens / Q000737:chemistry / Q000633:toxicity*
D058892:Adenosine Deaminase Inhibitors; D003839:Deoxyadenosines; D011684:Purine Nucleosides; D013723:Teratogens; D015649:Pentostatin; D007288:Inosine; D000243:Adenosine Deaminase; D000241:Adenosine; C058118:2'-deoxyadenosine