## 3 Results and Discussion
### Cd Exposure Schemes
#### 3.2.2 Cd Exposure of Dams during Lactation Period  
Eleven records analyzed Cd effects on offspring breastfed by dams exposed to Cd during the lactation days (Figure 2b). The research articles were published from 1997 to 2016 and most of the experiments were performed in rats (10/11). Although, experimental features in Table 2 show differences in the administration route, concentration/dose, exposure time, and effects some papers reported identical features, so these papers were grouped in Table 2. Cd in drinking water was the most reported administration route (8/11), then intravenous  
\begin{table}
\begin{tabular}{p{113.8 pt} p{113.8 pt} p{113.8 pt} p{113.8 pt}} \hline
**Strain (\(n\))** & & & & \\
**Dose/Concentration, Admin Route** & **Collection Time** & **Results** & **Year** \\
**Exposure Period** & **Organ Analyzed** & **Authors** & **Author** \\ \hline Wistar rats (\(n=6\)) & & Increased acetylcholinesterase & \\
50 mg CdCl\({}_{2}\)/L, d.w. & PD and PND 21 & and Na\({}^{+}\), K\({}^{+}\)-ATPase activities in the newborn rat brain that were ameliorated through a Cd-free lactation. & 2013 \\
20 mg CdCl\({}_{2}\)/kg bw, i.g. & GD 20 & External malformations in fetuses at GD 20 & 2004 \\ GD 6 to GD 14 (\(n=8\)), 21 & Physical and behavioral parameters & & delayed vaginal opening, and modified male and female sexual behavior \\ Wistar rats (\(\leftarrow\)) & & PND 84 & Cd dose dependently altered the spontaneous and evoked electrophysiological functions & 1998 \\
14, 7, and 3.5 mg CdCl\({}_{2}\)/kg bw, i.g. & Behavioral and neurotoxicological analysis & & the spontaneous and evoked electrophysiological functions & [PERSON] et al. [15] \\  & & Decreases renal alkaline phosphatase activity determined in pups fed by their biological mothers exposed to Cd. & 1992 \\ Sprague-Dawley rats (\(n=6\)–7) & & PND 3, and 12 & & exposed to Cd. \\
2.5 mg \({}^{109}\)CdCl\({}_{2}\)/kg bw, i.p. & Kidney, liver, and gastrointestinal tract & \({}^{109}\)Cd in liver at birth and in the gastrointestinal tract at PND 12 of newborns fed by their mothers. Prenatal Cd exposure cannot induce alone kidney damage & 1992 \\ Rats (\(\leftarrow\)) & & At PND 120 increased plasma and erythrocyte levels of MDA, reduced glutathione, activities of glutathione-S-transferase, glutathione reductase, and \(\uparrow\)[13] & 2008 \\
2 mg Cd(NO\({}_{3}\))\({}_{2}\)/kg bw, i.g. & PND 120 & & [PERSON] et al. \\ GD 6 to GD 15 (\(n=10\)), — & Blood & & \\
20 mg Cd(NO\({}_{3}\))\({}_{2}\)/kg bw, i.g. & PND 120 & & [PERSON] et al. \\ GD 6 to GD 15 (\(n=8\)), 24 & Blood & & \\
20 mg Cd(NO\({}_{4}\))\({}_{2}\)/kg & Blood & & \\  
(2/11), intragastrical (1/11), and intraperitoneal (1/11). Since Cd administration through the ad libitum drinking water was reported as a concentration, some authors estimated the dose consumed per dam by calculation of water consumed daily. [PERSON] et al. [19; 20] and [PERSON] et al. [21] described both the Cd concentration in the drinking water and estimated Cd dose. However, several authors, such as [PERSON] et al. [22], [PERSON] et al. [23], [PERSON] et al. [24; 25], and [PERSON] et al. [26], did not mention having estimated water consumption. In the lactation exposure scheme the highest Cd concentration was 300 mg/L and the lowest was 5 mg/L, while the highest dose was 4.8 mg/kg b.w. administered through drinking water and the lowest was 8.8 \(\upmu\)g/kg b.w. intravenous. Cd was administered as a single dose or daily during lactation and most authors described the standardization of litters at birth. All the authors reported that buckling pups were fed by their biological mothers. Effects of Cd Exposure during Lactation Period  
Dams exposed to Cd only during lactation transferred the heavy metal to their progeny by breastfeeding.