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exhibit extensive intracellular distribution of secretory granules (Kardong and Luchtel,
1986; Kochva, 1978). Interestingly, the secretory granules of
D. typus
and
N. tessellata
appear less electron-dense than those of
T. e. vagrans.
It is unclear whether this dif-
ference is related to level of synthetic activity, taxa-specific variation, or experimental
methods (Kardong and Luchtel, 1986; Kochva, 1978).
Kardong and Luchtel (1986) found rich unmyelinated innervations in the
T. e. vagrans
Duvernoy's gland, with bundled nerves encased in folds of Schwann cells. These were
commonly found within the connective tissue between acini adjacent to the basal lami-
nae. The authors attributed the flow of secretions to release of secretory granules into the
luminae, thereby creating secretory pressure that forces secretion through the glandular
channels (Kardong and Luchtel, 1986). Contraction of local bulging striated muscles
may augment secretory pressure (Kardong and Luchtel, 1986), as has been suggested
from study of
T. sirtalis
Duvernoy's gland secretion (Jansen and Foehring, 1983).
4.2.3.2 Summary of the Toxinology, Properties and Pathophysiology of
Duvernoy's Secretion from
Thamnophis
spp.
There is very limited information regarding the toxinology of
Thamnophis
spp.
Duvernoy's secretions. In a relatively early study, Vest (1981b) used aspiration as
well as micropipette extraction (see Weinstein and Kardong, 1994, for a review of
these methods) in order to obtain secretions from
T. e. vagrans
. He reported a yield
of 0.71 μL containing 0.057 mg solids. The secretion protein content was 46% (Vest,
1981b). Collection of Duvernoy's secretion from many non-front-fanged colubroids
(especially the smaller fossorial taxa) presents technical difficulties that can result in
contamination of Duvernoy's secretions with other buccal secretions and vice versa
(Hill and Mackessy, 2000; Weinstein and Kardong, 1994). Therefore, it is not clear
if Vest (1981b) assayed material primarily from Duvernoy's glands or, more likely, a
sample of mixed buccal secretions.
Other investigators have increased the yield of
Thamnophis
spp. secretions by
using parasympathomimetic agents, such as pilocarpine in sedated specimens (Fry
et al., 2003; Hill and Mackessy, 1997, 2000; Rosenberg et al., 1985). Using this method,
Rosenberg et al. (1985) obtained from
T. s. parietalis
an average yield of 3 μL secre-
tion containing 3.8 mg/mL of protein. With a similar method, Hill and Mackessy (2000)
obtained from
T. e. vagrans
a mean yield of 23 μL secretion containing 0.39 mg of protein
(51.6% protein).
To date, lethal potency studies have demonstrated low toxicities for Duvernoy's
secretions of
Thamnophis
spp. Vest (1981b) reported a murine i.p. LD
50
of 13.85 mg/
kg for
T. e. vagrans
secretions, while Rosenberg et al. (1985) reported an i.p. LD
50
of
33.0 mg/kg for
T. s. parietalis
secretions.
There are few data regarding the pathophysiological effects of
T. e. vagrans
Duvernoy's secretion in mice. Intravenous injection of
T. e. vagrans
secretion report-
edly caused “massive pulmonary hemorrhage” (Vest, 1981b). Additional hemor-
rhagic effects in other organs appeared to be dose dependent. Administration of
mixed buccal secretions devoid of significant amounts of Duvernoy's secretions
resulted in minor, diffuse local hemorrhage (Vest, 1981b). Myonecrosis has been
