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EC number: 202-597-5
CAS number: 97-63-2
The fastest rate
of absorption of MMA through rat epidermal membrane was recorded as
being 5688 μg*cm-2*hr-1 and this occurred between 2 and 8 hrs following
application of the chemical. The rate slowed considerably after 8 hours,
falling to virtually zero by 16 hours. Nearly half (45.5%) of the donor
reservoir had been depleted by 8 hours with 55% of the chemical
appearing in the receptor chamber by 16 hours. The rate plateaus after
eight hours, which is indicative of the donor reservoir being depleted.
methacrylate absorbed at a peak rate of 453 μg*cm-2*hr-1, between 4 and
24 hrs, with 10.2% of the applied dose having been absorbed during this
time. There appears to be a lag time with the rate of absorption between
0-4 hrs calculated to be 259 μg cm-2 hr-1. The rates of absorption
through human epidermis are considerably slower than those measured for
MMA through rat epidermis.
Whole rat skin
alkyl-methacrylate esters whose rate of absorption through whole rat
skin was investigated, methyl methacrylate is the most rapidly absorbed
chemical. Carboxylesterases present in the viable tissue mediate the
hydrolysis of these esters, producing the acid metabolite, together with
the structurally corresponding alcohol. In contrast to the larger
esters, MMA is not completely hydrolysed during the absorption process;
this is substantiated by the appearance of both the parent ester and the
metabolite MAA in the receptor fluid. Appearance of both chemicals in
the receptor fluid can be explained by MMA possessing a rate of
absorption that is higher than the rate with which it is hydrolysed.
The peak rate of
appearance of MMA, which occurred between 2.5-24 hrs was calculated to
be 360 μg*cm-2*hr-1. This compares to a peak rate of appearance for the
metabolite MAA, which occurred between 4-24 hrs and was calculated as
108 μg cm-2 hr-1. Of the original dose applied to the whole skin, 8.7%
appeared as MMA in the receptor chamber, while 2.6% appeared as MAA.
Therefore in total, 11.3% of the ester was depleted from the donor
The results of the whole-skin penetration studies and the model predictions for
other methacrylate esters are presented in the table.
Summary of the peak
rates of absorption of MAA & alkyl-methacrylate esters through whole rat
and human skin
Rat whole rat
Human whole skin
Peak rate of appearance (µg*cm-2*h-1)+- SEM
% age of
over x hours
The values in normal
type were obtained experimentally, whilst those in italics are predicted
** Values are
predicted rates of appearance of total chemical including parent ester
The in vivo and in vitro investigations as well as the PBPK models
developed from the data showed that alkyl-methacrylate esters are
rapidly absorbed and are hydrolyzed at exceptionally high rates to
methacrylic acid by high capacity, ubiquitous carboxylesterases.
Further, the removal of the hydrolysis product, methacrylic acid, also
is very rapid (minutes).
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